I am authoring apps on WM and this Microsoft Windows Mobile 6 based phone does not need a plan or even service to sync via USB or if you are so inclined Bluetooth.
If you are syncing via the cell phone companies network, YES that will die but activesync and WMDC will still sync when you connect the USB cable.
Hope this helps.
My 2-person company has 2 PDA/smartphones (HTC Fuse and Blackjack II) on an AT&T shared service plan. We are financially tight and I called AT&T today to terminate the wireless data plans on these two phones ($30 each/mo). AT&T now has a new policy (2009Nov01) that you cannot use a PDA/smartphone on the AT&T wireless network unless you pay for a data plan. The agent refused to terminate the data plans. One phone is currently out of contract, the other is out in Apr. I could downgrade phones but would lose the ability to sync with my computer. Any suggestions? Switch vendors? Any secrets to negotiating with AT&T?