As it was "mainly" the (Habsburg) family that suggested that Ferdinand steps down and a "new Generation" takes over, there are multiple possibilities.
A) Ferdinand stays in power - at least temporarily - as the Person of the Kaiser is not essentially to the further Course of the counter Revolution I assume the OTL history will not Change in the short run. Ist interesting that Ferdinand - once he stepped down - proved to be an excellent Administrator of his private property. I assume that Ferdinand will probably a bit less counter revoultionary than his nephew. Leading to a token parliament instead of returning to absolute absolutism
. The first test would be Ferdinands reaction to the Crimean War (FJ managed to antagonize Russia while not pleaseing Britain and France...). Here is assume that he (relying on the fact that he is an able Administrator) won't set up the 300.000 strong army FJ sent to Russias border, so the A-H economy does not suffer (which led to a delay of necessary changes to army Equipment) as OTL and Russia is maybe less antagonized. Which in turn would lead to the A-H army a bit better prepared to the following wars. FJ himself took command in the 1859 war against Sardinia and France - Ferdinand certainly won't do that - so ist possible that the war goes a bit better for A-H (especially if modernisations Long overdue and pushed back by the lack of funds - see above) will be done. Lets assume the Habsburgs manage to retain Milan and the other Habsburg states in Italy survive (i.e. no Italian unification for the next few years - or more?). This probably chnages also teh GErman unification (Milan was among the richest provinces).
B) Franz Karl (Brother of Ferdinand) takes over - honestly one worse Option - more interested in culture than something else - I assume A-H goes down basically the same way as OTL - Maximilian will take over in 1878 (if he dies as OTL). This allows a more mature man to follow an Emperor (mid forties) Max had no sense for economy, (needless to say as in line for the Empire he won't go to Mexico), but is more liberal - difficult to say how old he will get …
C) Maxx takes over - is declared as an adult - well Max as Young Emperor might be intersting - could do the same blunders as his brother, but likely is even more inclined for a liberal constitution - might save the Empire in the comon years (much like what I described under Ferdinand)
I would like to see a TL modelled after A- IMHO one interesting Option (if one Looks a bit over his bad OTL Image and sees what he could achieve privately)