No.
There are 3 sectors of astral (for now until more is unlocked).
S1-S2 drops level 65 gear.
S3 drops level 66 gear.
So you can go to s1-s2 and get level 65 gear and then upgrade it into level 66 gear later.
Or you can go s3 and get level 66 gear and skip that part about upgrading the gear again.
(You still have to upgrade from common/rare/epic/legend/mythic, but you can skip the large cost of gold and resources that it costs to upgrade from level 65 to 66.)
Hope that helps.
Also, refer to this quote for some additional information:
Yeah, you can turn a 65 into a 66.
Butttttttttttttt...
It costs weekly crap that is acquired from astral or whatever.
So
therefore, you will not be able to get full level 65 legend and then
all the sudden BOOM buy all this shit and turn into level 66 legend
because you will not have the required currency to do so.
I don't know the exact numbers, however, it will be something like this.
In order to purchase a level 66 legend from 65 legend it will cost you 2.5 weeks worth of currency you have farmed.
Therefore, you'll only be able to change ONE piece of gear from 65 to 66 every 2.5 or more weeks.
So this will actually leave you at a disadvantage if you continue trying to do this.