The SPX is already over half-way to the 10% target I had forecast in this post for the entirety of 2018.
When would it hit that level? It's anyone's guess, as anything seems possible in the current buoyant market environment. The momentum indicator is still rising on this long-term timeframe and is making new all-time highs in the process. Another 5% gain would send it up to that price, so we could be looking at a year-end target date to bring total gains of 11% by then...not an unreasonable expectation.
Another scenario is that it could reach that level around August of this year (pinpointed at the pink arrow shown on the second monthly chart below), which would put it at the +4 standard deviation level of a very long-term upward-sloping regression channel (beginning from the March 2009 low). That would give it plenty of "wiggle room" to allow for some price dips in between now and then. At the moment, price is in between the +3 and +4 standard deviation levels.
Alternatively, we may see a hit of 3000 (or beyond to its next major external Fibonacci level of 3047) at the +5 channel deviation level sometime in February, potentially taking the Dow 30 along with it to around 26,700 (as I described recently in this post). Subsequently, these indices may move sideways for awhile to allow some of this parabolic surge (that began after the November 2016 Presidential election) to dissipate.
Other factors to monitor, in this regard, are outlined in my above-referenced market forecast post.