By the time he fell ill Pericles was a broken man... He had lost his legitimate sons to the plague and also his will to live after this disaster... Had he survived he would have retired anyway...
From a psychological perspective you may have a point: the plague wasn't just a material blow (though it was a huge one), it severely hampered the morale of the remaining Athenians.
But what does he do next? He wakes up one morning to discover he survived the plauge. That's bound to lift his spirits. Let's say he does decide to "retire" for a while. Probably this means that he doesn't think it fit to risk his political reputation so soon after the plague has hit. Now, the Athenians might not let him: if nothing else, Pericles couldn't risk letting any of his potential opponents (Cleon and Demosthenes, for example) ostracized him.
An ageing Pericles will thus probably either 1) be forced to fight off Cleon or 2) take advantage of Cleon's inexperience to rise to prominence later. Pericles' strategy from the beginning was probably too defensive to avoid a victory, since he seemed to want to confirm "arbitratrion" (as outlined in the 30 Years Peace that ended the First Peloponnesian War) as a new method of settling political disputes between Athens and Sparta. Hence, he would naturally oppose Cleon's more aggressive, confrontational approach.
Many of the mistakes Athens made was a result of its very fractious politics after Pericles died; note these politics were
more fractious than usual and parallel US politics in the 1850s, for example: the very nature of political associations are changing and established methods of settling political disputes are failing. Just having Pericles survive as a force may change a lot of that. For one, Nicias while a decent general (if overly cautious), was a bad politician and a horrible negotiator. Even if Pericles survives and is old and dottering, the very fact of his survival changes the nature of these decisions.
For example, say Pericles takes an inactive role and finds himself forced to allows Cleon and Demosthenes to take most of his OTL actions through the seige at Pylos and Sphacteria. Would Cleon still end up being dared to go to Amphipolis? It was an iffy thing to begin with. Let's say he doesn't, because Demosthenes and Nicias have a joint command. Then there will have to be a battle of some sort between Brasidas and the Athenian force. I'd expect that if the Athenians can force a battle they
might be able to win, since Brasidas didn't have a major force with him.
Even then, Periciles may have tried to force a peace negotiation just after Pylos and Sphacteria (when Athens captured Spartan soldiers) rather than wait. This would preclude Brasidas' expedition and keep Athens in control of Amphipolis. Corinth and Thebes would fume, but Sparta would have her peace and her soldiers back. And Pericles' continued survival would at least have allowed Athenian political factions to re-organize around him (and opposition to him).
Hence, I'd say there's a good chance for peace around 425 on something like the terms of 421, but with Athens in control of Amphipolis.
Events thereafter may still re-ignitie hositilies: Corinth will bristle at Athens' dominance and will keep trying to keep the war going, as she did after 421. Argos' peace with Sparta will still expire in about 418, leaving a potential foothold on the Peloponnesus for Athens.
The slam-dunk for an Athenian victory is that with Pericles' backing, Alcibiades can better manuever for an alliance with the Argives (under the general principles of the 30 Years' Peace, no doubt confirmed by the Peace of 425, that non-alligned states could freely associated with one of the two power blocs). Worse case, there's a revolt in the Northern Aegean that Athens quickly puts down: maybe Pericles even gets to lessen the tribute imposed by Cleon's increases (or maybe he precludes is, lessening resentment). Hence Athens has an alliance with the Argives, but doesn't have the trouble of the pretense of a Spartan Alliance. Even if there isn't a battle, just having the Argive alliance will probably keep Sparta from attacking. If that alliance does provoke a battle, Athens can probably win it it.
Corinth and Thebes will still fester, but Athens plus Amphipolis and perhaps Argos is a lot more imposing. It will probably keep the Persians from interfering in Greek affairs for a while.
The question is as before whether Athens can avoid decisions which create imperial overstretch. There's potential that the Empire could create loyalty amongst the subject populations, given time, by providing employment to the poor. However, Sicily and Cyrus will still present pretty major opportunities to blunder in a big way. Odds are, they will, since unless Athens can alter the strategic circumstances (cement a strong alliance with Corinth, Thebes or Sparta that sees the circle of Athenian alliance become an effective means of panhellenic policy) any blunder will allow the rest of Greece to redress the balance of power.
In any case, I highly doubt that even a seemingly "retired" Pericles leaves history unchanged, for the earth shattering effects this will have on Athenian politics. Additionally, if nothing else, the POV of Thucydides histories may change if 1) he's not exiled and 2) if he can interview Pericles exhaustively.