Yes, status earned through stays in 2011 would give you HH Diamond status for the rest of 2011, all of 2012, and the way the Hilton "year" is defined (for status) through March 31, 2013.

It is an individual decision about whether it makes more sense to get status in another program versus trying to maximize your point earnings in Hilton HHonors. As others have mentioned, a big part of the decision is about your specific objectives for award travel. Other considerations include: your ability to earn HH points other ways (e.g., through credit card spend), how many points you are earning with your current travel, and what Diamond benefits you are getting from the hotel(s) you are staying for your business travel now.

When I was travelling weekly for business, I was staying at inexpensive Hampton Inns, so I wasn't giving up many points or benefits if I diverted some stays to another brand. What I would encourage you to do, though, is if you decide to try to get status in SPG or Marriott, that you request a status challenge from these programs. This approach will allow you to obtain top status with far less stays. There is more specific information about status challenges on the SPG/Marriott forums.