No, not completely. I was surprised (as everybody, I think), but the withdrawal is only a partial one. Looks like the increase of the airpower which has been made some time ago (don't remember the date) is now taken back. To announce such things loudly is, of course, thought to be helpful for various diplomatic reasons.
There are, I think, several reasons why one needs less airpower now.
After the Turkish attack against the Russian plane, it was necessary to demonstrate additional power in Latakia. To punish the Turkish terrorists (these were not only Turkish-paid Al Qaida, but a lot of Turkish Grey Wolves and so on). And for this purpose, some additional aircraft, in particular also aircraft for protection of the bombers, have been moved to Syria. The job in Latakia is almost finished now, so no more airforce for Latakia necessary. With Latakia and the jihadi highway closed, there is much less necessity for bombing near the Turkish border. Near, say, Deir Ezzor or Palmyra one does not need protection from Turkish airforce.
During the offensive against the jihadi highway, they have attacked some very seriously entrenched and protected defense lines. Because this was a very serious, if not the most serious, connection for Al Qaida, and because an attack had to be expected in this particular place, because the Syrian aim to break the siege of Nubl and Zahra was obvious. What I have read, the attacks against this particular front line have been very intense. And I think that the aim of this very intense attacks was also a demonstration for the future, for the various fighters of various rebel groups. Those who have survived this explain what this means. (Note: this was close to Aleppo but outside Aleppo. There was no point at all bombing Aleppo itself. This was left to Americans, who have bombed Aleppo itself.) But, once done, this extension of airforce power is no longer necessary. Some reduction makes sense.
In other words, with the liberation of Latakia, the cut of the jihadi highway in Aleppo, and the ceasefire where was simply much less need in airpower. And aircraft standing around without any need at the moment.
The third point is a diplomatic signal to all those rebels who participate in the ceasefire. It is a sign that Russia is really interested in its continuation.