For those of us worried about Locking into a "holder" 4G Device now just so we can keep 4G when the Bionic Comes out after Tiered Data Launches 7/7, It has been CONFIRMED that if you have Unlimited 3G Data Plan now and Upgrade Later, You WILL be locked in unlimited 4G. So there is no need to go out and buy a T-Bolt, Charge or Revo just to lock into 4G for the Bionic Release.
Verizon Support: 3G Customers Upgrading to 4G After July 7 Can Keep Unlimited Data - Droid Life: A Droid Community BlogOn our quest to try and provide you with as many different upgrade situations as possible that will allow you to keep your unlimited data plan after July 7, we may have another to add to the list. This is one of those that many of us sort of figured would be the case, but with rumors swirling about and no official mention in any of the pieces we’ve reported on, we weren’t 100% sure. Well, according to @VZWSupport (the official Verizon support account on Twitter), if you are currently locked into a 3G unlimited smartphone plan and will more-than-likely jump to a 4G phone after the July 7 tiers begin, you will still be able to keep your original data plan.