Tychy is set to make three B-UVs: One Jeep, one FIAT, one Alfa (a second FIAT seems to be gone, but it could come back). The plant has produced up to 600,000 units a year flat-out, but dealing with a mix of platforms, or bigger cars, would probably reduce that figure. Currently around 250,000 units (Ypsilon and 500) are made in Tychy every year. If you give each of the new UVs a modest 75,000 sales each, they could comfortably co-exist with the existing products. But if one of the new cars becomes a hit, then one of the older products would have to end, or move, in order to free up space.
There’s also regulatory forces to consider: if Stellantis wants to keep making 500 ICE and Ypsilon after May 2024, it will need to add a lot of safety systems to the cars (driver attention monitor, speed-limit warning, autonomous emergency braking, event data recorder, facility for fitting an alcohol-detector interlock). That’s a lot of cost to retrofit, but all of these are in place in the e-Mini architecture used in 500 electric.
Whatever happens about site of manufacture or platform, I think 500 ICE, Panda and Ypsilon will now be updated. Covid and the chip-shortage has delayed the whole market by at least a year, with the result that now 2024 is too soon to completely stop making ICE models in the A-segment - and the A-segment is essential for FIAT and Lancia. (There’s no suitable PSA design for A-segment)