I can't imagine why you'd even need a cellphone upgrade if your app needs are so basic.
As for Samsung ditching Android, as much as I'm sure they'd like to be able to do that it isn't going to happen and it makes no business sense. Tizen is nothing. It's suitable for $50 phones and 'smartwatch' type gadgets, but not for full-fledged smartphones and tablets. And given that Android continues to be free and provides them with an enormous app store to leverage, there's no reason to leave Android at all.
Aside from the odd occasion when I do see a truly useful app it is more the hardware specs (Fast performance, Camera/Movie Quality, Storage, Functionality) and "gadgetry" features that interests me more. Thus while there is no reason to leave Android in particular there is nothing keeping me to it either should another free equivalent or better OS come along. Supporting it because it is free is a plus, but I'm also prepared to pay fairly for quality if I feel it is fair.
If I see that the Mobile OS (Ubuntu?) that converts your phone into a full blown Linux station become a reality and it has the hardware to back it up, and it supports the same apps I regularly use, I might be interested.
Android might not have much more to offer, it just gets prettier or slightly more snappy. I feel the hardware is where it is all about and thereafter the first OS to support it or hold it back will get my vote.
As an example the first production phone that can roll out into a tablet sized device will grab lots of attention arguably despite whatever OS is used. Things like this is what I am keeping my eye on. Already my Note II (Android) can dock and display on my TV/LCD and be used with a keyboard and mouse. If Android keeps the pace, then I guess no issue

if they don't then hopefully Samsung have a backup plan.
I guess what I am trying to say is Android in particular does not have any major unique "selling point" in itself other than it is free and open. Perhaps that it integrates with Google is a key point as well. I hear developers hate Android because of so many random issues with the vast number of different phones out there.