As of this writing, Microsoft has only announced Wi-Fi connectivity for its new Surface tablet and I'm guessing it will stay that way for the time being, especially in light of the new shared data plans coming soon to carrier near you.
Verizon Wireless has already announced its Share Everything plans. Add a tablet to that plan and you'll pay $10 extra per month. Connect a Wi-Fi-only iPad or Surface to that plan with your smartphone's hotspot and it won't cost anything more than the data you use.
Industry analyst Chetan Sharma estimates that six out of 10 tablets sold are Wi-Fi only, that's revised from initial estimates of nine out of 10. Maybe I’m wrong, but I don’t see that ratio changing a great deal in the near future.
Microsoft hasn't coughed up pricing details for the Surface, but consider that an LTE-capable iPad costs $230 more than a Wi-Fi-only model. I suppose it depends on how the other carriers approach the shared data plans, but if they stick with Verizon's tack, I can't imagine too many consumers are going to be persuaded to spend the extra cash for a cellular-enabled tablet when they can simply tether to their smartphones.
No doubt, tablets are here to stay. They're useful in any number of situations, but they're not a smartphone. The use cases for the tablet are primarily in areas where Wi-Fi is available. Perhaps the car is the one situation where this isn't possible, in which case we return to the hotspot or tethering capabilities inherent in the smartphone.
My point is that the Surface certainly won't suffer in competition with the iPad for lack of an LTE modem. Perhaps the best thing this tablet has in its favor is that Microsoft's overall mobile strategy so closely resembles Apple's. In the same way that Apple's iOS and Mac OS X have a similar feel, Windows 8 is meant to unify all Microsoft devices (desktop, laptop, smartphone, tablet, XBox). The jury is still out on whether Microsoft's consumer-facing cloud solutions have what it takes to compete with iCloud.
All of these considerations aside, the real question is whether there's room for another player on Apple and Google's court. You have to admit that Microsoft, with the Surface and Nokia in tow, are certainly making a much better case for itself than has Research In Motion in recent months.