I am assuming that in most leagues he will lose his SS eligibility. Does that drop him out of the number 1 spot? People still draft Pujols at #1, so I would say that it depends on what you want. I do not think anyone took Soriano number 1 in any leagues this year, but they might next year if he is hot the rest of the way and Arod loses that SS spot. Then the top four picks will probably be a scramble of Vlad, Pujols, Soriano, Arod.
For a keeper league though, you need to find out the rules of your league eligibility next year and plan accordingly. If you have him at short now, I would consider trading him for a 3B and SS. But do not over react and trade him low, the guy is still a monster. It would be pointless though to trade him for Beltran or Pujols or Manny unless you think they have just better overall numbers. Those guys do not help position scarcity at all.
I think this is a very important question. In my opinion, 3b is deep. Really deep. Blalock, A-Rod, Rolen, Lowell, Ramirez, Chavez, Tex, Huff, Mora, the list goes on. D. Wright will soon be there.
I drafted A-Rod first overall in my dynasty keeper league, and I'm starting to think he might not be a top 5 pick next year. It depends on how strong his second half is, and if he keeps stealing. If he does, an argument certainly can be made that he should be the first overall.
I've considered dealing him this year, but I have been hesitant because he certainly can be the best fantasy player around when he is locked in. I'm not sure where his value lies for the future, but if you can get him for Manny, I'd do it in a heartbeat. He is capable of matching Manny's stats this year with an additional 25 SB's.