First of all, I don't know if we need to wait until Fedora 26 gets branched from Rawhide (2017-02-21). It might be too late to get Mono 4.8 into Fedora 26.
Apart from that, I am at least trying to do scratch builds for the first release candidate for Mono 4.8, 18.104.22.1689 https://releases.xamarin.com/beta-release-cycle-9-rc-builds/
I will report issues here that happen for the scratch build.
I have the spec file and patches here: https://github.com/tpokorra/lbs-mono-fedora/tree/master/mono
The scratch build https://koji.fedoraproject.org/koji/taskinfo?taskID=17276095
worked for x86_64, i686, aarch64 and armv7hl.
for ppc64 I have filed this bug upstream: https://bugzilla.xamarin.com/show_bug.cgi?id=51573
for ppc64le I have filed this bug upstream: https://bugzilla.xamarin.com/show_bug.cgi?id=51572
both bugs have the build log attached.
*** Bug 1426201 has been marked as a duplicate of this bug. ***
seems the bugs for ppc64 and ppc64le have been resolved upstream. I don't get the build errors anymore.
We now have Mono 4.8 in Rawhide.