Nokia phones running android will be likely to have two year OS updates and three year security updates, take into account that from now 2018 nokia hmd will be adopting Android One program which make easier to address that kind of questions more easily. In 2016-2017 HMD said their android phones will be running up to date, fast, secure, up to date, clean UI but never said for how long (it is obvious android phones will not be able to run the latest OS from google due to technical reasons and market reasons...phone manufactures do need to sell devices...so upgrading them forever does not make sense from a profit point of view)
I believe it could go beyond that due to Project Treble. However, this will be heavily dependent on Qualcomm.
Don't think so. Guaranteed 2 major versions. For the Nokia 5 that will be O and P. But, maybe you're lucky.
I have no problems with the updates. Since April, every month a security update.
Probably to busy with releasing new models and/or Android P.....
Well, I still have faith in HMD in this one :-)
September/October at last (I hope).