I use my tablet to supplement my desktop and vice versa. Most tablets these days could replace other form factors for light duty computing. But the MS tablets are still lacking the CPU/gpu power to truly replace a desktop gaming machine, not to mention, most tablets aren't exactly user friendly when it comes to upgrading hardware.
In the near term, no, I can't see the surface pro replacing towers. laptops, maybe, but it'll be 5-7 years before these are powerfull enough to make me think twice about getting rid of my tower. And even then, the desktops will have increased in power enough to warrant them staying in use for serious gamers.
CPU: i3-3225 GPU: ASUS HD 7850
RAM: 8gb G.skill Disk: 128SSD 2x1TB in raid 0
corsair h80 Power: 500w ASUS p8b75 mobo