Wow, 5 months is an insanely short timetable to ask people to migrate entire systems to another vendor. I’m surprised their contracts don’t have better terms.
I also have experience running SmartOS on Leaseweb (they purchased Uniquity Hosting where I setup SmartOS instances on numerous servers in numerous datacentres.
Decisions like this are long in the making, this is just the public announcement for the rest of us.