It's a standard practice when a new release is upcoming that all the engines that aren't going to be part of the release get disabled for daily builds.
So SCI won't be officially supported for the 1.0 release? Why would you choose now for such an important milestone when one of the most highly anticipated updates in ScummVM history is right around the corner? I know it's only a number, but still . . .
Well there had even been some discussions to for the "1.0.0" release by the release cycles for older releases. Back then the missing manual was the main reason not to do that. Since it turned out, that we probably have to wait forever to the manual to finish (even though there seems to be some work on it recently), we decided to just name the current release 1.0.0.
Also the SCI engine might have some regressions over FreeSCI AND of course FreeSCI itself was not perfect, so before SCI will be 'finished' there'll be still a long time to pass. On the other hands the SCI team has some plans to announce some selected titles as supported for the next release (thus 1.1.0). Of course those might be only a few games, not the majority of SCI games.
Personally for me including SCI would be one of the last reasons to wait longer for a 1.0.0 release. I think some missing (and in the works / nearly finished) features for SCUMM (and other existing engines) would've been much nicer to have in 1.0.0, like TFMX for MI1 Amiga. But I can understand why we chose to release this one as 1.0.0 and I think it's fine.
And just FYI we make this release 1.0.0, because if we wait for "nice features around the corner", we will probably have to wait forever to release a 1.0.0. After SCI is 'done', there's probably another thing people would like to see in ScummVM 1.0.0, which is in the works by then.
Also you have to acknowledge that ScummVM is not intended to always add support for new engines and thus waiting for an engine to be finished is probably a pretty weak argument against a major release. SCUMM itself misses some features and still it is pretty mature and probably like 80-95% of the users out there don't expire any problems / missing features, so this is a far more important point to consider about 1.0.0. And last but not least the project is named ScummVM, thus it would be strange to have a milestone for the first major release to be set on support for SCI ;-).