A cursory search tells me there's an update to 1.05 which is about 400MB. Assuming there were versions 1.01-1.04 before it, and each one was at most 500MB in size, you're looking at a possible total of 2.5GB of patches. Assuming the 1GB of storage that comes with the Vita is required for system files and that those files must be transferred to the new card, you're left with 0.5GB of free space. A little tight, but it would probably be fine as long as you don't have to download anything else and save files for the game aren't ridiculous.
Those are all very "worst case scenario" numbers; it's possible that the 1.05 update was a straight jump from the release version, in which case you'd have more like 2.5-3.5GB of free space. Plus I don't own a Vita myself (basing this off of the PSP I used to own) so I'm not sure how it manages its files.
TL;DR I'd get the 4GB card first, only purchasing it after I have the game and Vita in hand, and making sure to buy it from a reputable retailer with a good return policy. Once it arrives I'd immediately test it to see if it fits the patch(es) and save files: if it works, great; if it doesn't, RMA the card while it's still eligible for return and get a larger one.
last edited at Jul 23, 2016 2:13AM