You shouldn't lose data because your data is over 4GB. Yes, if you change to SQL Server 2012, you would lose your support. SQL will allow you a grace period past 4GB, but it is difficult to know how much that will be. But, at that point, you should have read only and no write, but you shouldn't lose data. It's not as if, SQL purges data and adds more.
I wonder if it is an issue of 32-bit addressing. Besides the actual size of the DB, there is the indexing tree and the database caching that also consumes memory.
