I think no company can guarantee they will be around, or that their services wont change forever, I am sure that is Hologram’s plan but no one can see the future. And any “guarantee” on the help forum is pretty useless anyway. What it seems like you want is a contracted service agreement which Hologram may do for enterprise customers but probably not small deployments.
The thing you can control is implementing an ability to do remote software updates on your devices, there are many reasons you may want to do this, Hologram changing their API only being one of them. For a deployed product with limited or no future access I think this is kind of a necessity.
With this ability you can at least react in the rare case Hologram changes anything on their end and more likely, fix bugs, add features, etc. as needed (I know I thought I was “done” with my software and have pushed updates about 1-2x a month the last few months so was very glad I decided to implement over-the-air updates)
Secondly if you want more control over the features / guarantees / lifecycle of your cloud endpoints you can make your own or use one of the giants services like on AWS or Google.