In 20 years time any four stroke that is still running will be collectable.
Cannondales & Vertamati's would be on my list.
Being reliable or competitive isn't part of the equation for being collectable.
Mainstream bikes would be the last 2 stroke made, assuming that happens.
The first electric bikes would make collectables too as I’m sure that in years to come these will be refined to be a lot better than the current offerings