App-Store Lock in is nothing new
the same type of 'lock in' exists in the computer and video game console market. Playstation 2 games don't play on Playstation 3.
There is nothing stopping App owners to keep their old phones for the 'backward compatibility'.
Another example: I moved from a PC to a Mac and had to repurchase MS Office for Mac, it was also part of a tech refresh so was ok. One could also argue that App-Store purchases are dwarfed in price compared with traditional software and video game prices.