Should there be? Guess that's a matter of opinion.
Personally I don't see any real reason for MS to have a handheld. My view is MS is only interested in providing devices where they feel they need to in order to support their software in the marketplace or as a platform to compete with others (Xbox vs Sony, Zune vs Apple for example). I don't believe they are ever in it for the hardware though - they want their OS and standards in play and when a market isn't using them or is being overrun by a company not using them (again, for example Sony with PS2 or Apple with iPhone/iPod were both terrible and dominant platforms from MS perspective using little to no of their software).
Hence their obvious interest in a mobile OS and the handheld market and tablets. But a dedicated gaming handheld? I just don't see it fitting the company focus and approach. I guess some gamers would love an Xbox handheld to link to their console but I just don't see MS being interested.
TBH I'm still not sure MS would even be producing their own console if Sony and Nintendo ran MS OS and infrastructure in a similar manner to the PC market. For me hardware is just a means to an end for MS, and in the case of a dedicated handheld their is no real endgame or need for them.
Mobile in general is a different matter of course - hence their big focus on that at the moment.
So no, not unless gaming handhelds started to rival smart phones and tablets for general social and interactive use vs primarily being closed loop gaming systems. I guess Vita is trying to be more social so it might be interested to see how it fares, but for the moment I'm saying no.
Try to be reasonable... its easier than you think...
