I am currently paying $70 for a smart phone plan. It was a bad choice, but one I am locked into for awhile longer.
If I can buy a good plan with the Tab, I'd be fine with using it with either blue tooth or in speaker phone mode for the small amount of voice calling I do. If I suddenly wanted to use voice calling a lot more than I do at present, I could always go with a basic phone on month to month. If the TAB is available WiFi only, that would work for me, too.
It will make sense for some people, not for others.