This is not looking good.
Yesterday, Bleeding Cool posted an article noting that you could no longer subscribe to the comic via Archie's website. As you can see there, no Sonic options. This is also the deep link for the Sonic The Hedgehog book and Sonic Universe, which again, is missing the option to subscribe.
Earlier today, Sonic Stadium user doctorbenMD called Archie to get some more information and was told the book may be ending at 290. This is far from fully confirmed but if so, looks like the book was dropped suddenly. Archie nor Sega have made a public statement yet. I'll update this as more information comes.
Some more reading on this:
Update: Jan 23 2017
There still has been no official word from Archie regarding the cancellation of the comics however, new solicitations have come out. This will be updated when subscriptions have been resolved.
Update: Feb 22 2017
Archie has not released any Sonic solicitations for May. In addition, issues 291 and 292 have been pushed to April according to Previews World. Sega and Archie have maintained a stiff lip for now.