Will it be possible to switch from systemd to upstart from 15.10 onwards?

In Ubuntu 15.04, it is possible to switch from systemd to upstart. Will this ability be retained going forward?

Unlikely anyone will be able to answer this based on facts but I would assume that ...

• switching from GRUB like you can do now (at run time) is likely to disappear and this is also likely to happen when 16.04 LTS arrives. During the Ubuntu Developer Summit (UDS 14.03) Mark Shuttleworth announced that systemd will be used as default on the next LTS version of Ubuntu, Ubuntu 16.04.

• but as long as the package is available you can install it yourself. 15.10 still has upstart. How well new services will be supported by upstart is anyone's guess. Even I myself doubt it will be supported.

So I assume the answer is yes but with increasingly difficulty. I would forget about upstart and get to know systemd. In this case I would advice to not swim against the current.