I disagree. If he is going to pick a minority like Jindal, or a woman like Palin, then I think it makes better sense to announce it soon to get people talking about it, steal some of the nonstop 24/7 coverage of Obama in the media, and generate some excitement in the lead up to the conventions.
I would agree with waiting right up until the convention if McCain had been running anything resembling an effective campaign, but he has been virtually invisible to this point. Announcing now, under the conditions I just stated above, would give this "campaign" some very sorely needed positive attention.
I think the Palin pick could work, I really do. But I’d want Obama committed to someone dull like Tim Kaine first, before rolling her out.