There have been rumors around for several years now that multiple master fonts might not be gone completely, or that a new solution might be in the works. Nick Sherman wrote a long, but exciting article about the new possibilities on A List Apart. Superpolator (on the left) shows some exciting possibilities. My personal hope is for OpenType features in ePUBs.
Variable type has some big guns behind it
Recently, Adam Twardoch made a proposal along these same lines. This is a big idea because Adam is one of the major designers working on the next version of FontLab—which we must assume is in the works. FontLab 5 has been out for a long time now.
Can variable type be added to ePUB3 & beyond?
I have no idea, but it could solve some real problems we have typographically with our digital books being read on everything from smartphones through phablets to iPads. This will bear watching. I’ll let you know if I hear anything. As you can see above, these possibilities could help a lot. Maybe we can even get OpenType features working in our ePUBs.