As for now there is no definite answer as to whether Exchange 2010 will work directly with NTBackup. If you look at the Exchange 2010 Backup SDK it indicates that Exchange 2010 will remove the ability to do streaming backups, which is what NTBackup currently uses to backup Exchange, and will require block level backups, so if NTBackup is to work with Exchange its going to need to be able to do that. This said, this is the same reason you cannot do Exchange backups in server 2008, so if they are fixing that in the next SP, then it should work for 2010 as well, unless they are just re-enabling streaming backups in 2008.
This said, Exchange 2010 does have a very comprehensive backup SDK so if NTBackup does not work I'm sure there will be plenty of people writing solutions to solve this, or alternative applications to do the same thing.