That's probably wise
Nintendo and Sony seem to have a lock on the dedicated gaming handheld scene, with the former doing much better than the latter. Of the three major console manufacturers, Microsoft is the odd man out, as it's never shown any serious interest in entering this market. That doesn't look set to change anytime soon.
Newly appointed head of Xbox Phil Spencer took to Twitter to shed some light on Microsoft's position regarding this matter. When asked about the possibilities, Spencer said "I don't think we'll do a dedicated handheld gaming device, rather just focus on WP, tablets, maybe with controller support someday."
Microsoft may have been successful once in barging into the gaming scene in 2001, but the timing is probably far from right to try to recreate it with handhelds. At the very beginning of a new console generation, Microsoft would be better served to focus on bringing up the adoption rate of the Xbox One instead of spreading themselves even thinner by launching another new product.