Preparing on which base of information?Jennifer W wrote:thinking it is actually time to start preparing for a need for the fallback option or better yet, seeing a need to do so.
No Unity: Not of interest for Mint, never was.
Gnome as default DE: the same.
Those possible plans, where not even the smallest hint exists? Not a base for any decision.
As I wrote already: The question is, what did Shuttleworth not say and what else will change? This can be to the positive or to the negative, but at this time this is all speculation. Perhaps Ubuntu 17.10 will give more hints. Or somebody is able to extract more information from Shuttleworth ...
If - hypothetically - in one year Ubuntu 18.04 should display as being not more suitable as a Mint base, than there is at least 1 year left for Mint 17.x users to get a new Mint base for Mint 19, Mint 18.x users have even 2 years more time. The current versions will not stall at this time.
BTW: those, who are really affected on the first place, if things should go really bad, are the Ubuntu users. Hardly to believe, that there will not come a loud reaction.