Should i buy a phone for minecraft or wait for march for the ps vita version?

You might as well get the Vita version. You'll find the mobile version too limited. If you're still not sure, play the demo of the Pocket Edition if you decide to get a phone.

Phone, the pocket edition can hold more like in the next update will have infinite worlds for pe and the ps vita version can't handle infinite worlds

Buy the PC version, I personally hate the pocket edition, so if you really need to choose between the two. Choose the vita