It would be lovely to see them back in the mobile arena with Windows devices, though I'm guessing that they don't have the asset strength to be able to do this. I've had some wonderful devices from them, including the N95, which was ahead of the field.
I'm not a fan of Microsoft's drabber phones, stopping those brightly coloured Lumia cases that allow me to find it easily, if I've misplaced it. Their strategy towards the corporate/business sector, away from the consumer sectors in various countries, apparently the reason for universal drab. It was Apple's move into brighter, shinier tech that supported them being viewed as cooler than the grey pc market of yesteryear. Microsoft is certainly innovating now, albeit reportedly not doing much new themselves with mobile in 2016 - although OEMs will get the chance.
I assume that there must be millions of people globally who would trust a Nokia return into mobile. Whether enough of their original staff would do the same is another matter. (I'm assuming that some transferred within the Nokia business, rather than transferred over to MS, so they may still have some great in-house expertise).