It may be the wish "to become", yes. But I wouldn't feel that it is a wrong thought, it just may be that if you want to be reborn again and again, you will probably miss the chance for enlightenment at that moment of death. This is how the teachings go, but I don't know personally. But it could be a right thought to wish to put our mind towards a good object so that if there is rebirth, it will be a beneficial rebirth. That is not a wrong thought. So, I would probably wish to channel that wanting to be reborn into a more specific type of wishing, if one doesn't feel that one has the capability of letting go totally at that moment. Rather then having desire at that particular moment, to rechannel it into a suitable meditation object so that you produce the causes for it, rather then just wanting it.