The Mac Mini would not even be a consideration in the "I can take on the go" field. It is not a portable, in the true sense of the word, it is just a very small desktop machine that requires a keyboard, monitor and an external power brick.

Rumors of a "think" MacBook (Pro or otherwise) are just that, rumors. Apple is not in the habit of announcing future computer lines until they are available for sale.
The MacBook or MacBook Pro will easily do all that you ask, maxing the memory is always a good idea, and that includes XP and Vista.

Yes, it is probably wise to wait for Leopard which should be out before July, but who knows?

P