Anyone heard of an unlocked 8900 that is being tested that will not require a phone or data plan, but rather use wifi for data?

Heard? No.
Likely? No.

not likely to happen.

Any idea where it is being tsted?

Alright, I will come clean. Im in the process of testing one right now. So far it seems to work pretty well. You activate email through the desktop manager. You want to make sure you dont have a SIM in it when you first connect to the wi-fi, for some reason it doesnt like it. It is the standard 8900.

I am currently using it with a TMobile SIM as well. The UMA is not enabled on this device because that is a T-Mobile only thing. It will be available through CDW. This device is designed for those companies that use shift workers who never leave the building.

i have one in my hands at the moment, if you mean by unlocked that you can just use it without a provider specific SIM card....
in Belgium carriers are not allowed to use SIMlocks, therefore all phones we buy here are SIMlock free

I believe the OP is using one with no SIM card at all.
Not unlocked in the normal use of the term.

yeah this is completely unlocked. No SIM required. Hook up to your computer to get your enterprise activation and presto! your wifi is your data connection. It has been pretty cool. the back is black not grey like the T-mobile. Runs on unsecure and secure networks. So anytime you have wi-fi you have data. I took some pictures with a crappy WM phone, but will post them anyway. The camera is a 3.2 mp. The volume on it is outstanding. Been playing Slacker radio at work, and even at the lowest setting it is almost too loud. It has the ability to adjust Bass and Treble while you are in a call. All of the "standard" features are here.

Didn't Earthlink fool around with something like this a while back? WiFi only? Not a big success IIRC.

RIM 7270. Google it.