No, they won't. Congress will tell them since they already have four small carriers, they don't need more, even if they are bigger.
Thing is, this is cruiser tonnage. The carrier tonnage can only be used for carriers, but the London Naval Treaty, which the Congress
ratified, explicitly allows for a certain percentage of cruiser tonnage to be built as hybrid
cruisers, not carriers. These ships would likely be laid down late 1931 if they were ordered, pushing back some of the
New Orleans class a few years.
They do not take up carrier tonnage, and the US would still need to use the entirety of its tonnage there. There's nothing else they can spend the allotted funds for, as there is a battleship holiday going on. There's nothing else to spend the money on, and the cost would likely be cheaper up front than OTL to boot as aircraft carriers costs are skewed towards the long term. After all, the US hybrids were counters to cruisers (esp
Panzerschiff) while still being treaty compliant - they do not match up to Japanese carriers.
So if Congress is willing to not build up to treaty limits in the one capital class vessel they can construct in the early 30s because of an alternate
cruiser design, there must be other issues at hand or the Japanese are no longer such a threat.
10,000 tonnes of hybrid is always going to be worse than 10kt of cruiser or 10kt of carrier. But is it better than 5kt of carrier and 5kt of cruiser (approximately an Atlanta and a Casablanca)?
Anyway I think (without any evidence...) the Flight Deck Cruisers were intended to be converted into proper light carriers (ending up like the Independence class) in the event of war. Lift the turrets, razee the superstructure, extend the hanger/flight deck, new superstructure etc.. This might take a short as six months, much quicker than building new carriers. 20kt of Yorktown gives you an air group of 90 vis 70 for 22kt worth of Independences, which doesn't seem too bad. 20kt of carrier is more useful than 20kt of cruiser in nearly all WW2 circumstances.
Apologies in advance for the poor wording.
Hybrids as a type were considered all the way up until the late 30s, even in the era where the treaty had been abrogated and the US was planning on exceeding the 10k ton limit. The landing strips were longer, but the sentiment remained (aircraft gained a lot more of the vessel than previously). The type wasn't abandoned as tonnage limits were abandoned, however, so I doubt that the vessels would be converted upon immediate entry.
They still maintain a role scouting, and are good vessels to use for escorting until dedicated escort vessels are built. If the war is anything like OTL, the US will be starving for decks - yes they could convert these vessels, but they could also use what they have for now while better built, larger light carriers are constructed.
If one of these warships is greviously wounded but makes it back to port, then yes, they will likely be converted as they're going to be there anyway. But the importance of using existing assets would outweight converting the old vessels unless an availability of such length occurs.