Don't count on Friday being down. If you want to buy more stock, do so. While no one knows the future, the price on Friday is not likely to be appreciably less than it is now and it could be appreciably more. There were people who were "waiting for the drop" at $500 and they're still waiting...
If you don't want to pay current prices for whatever reason, that's fine. For example, I decided I was too heavy on $TSLA and put money elsewhere. If the shorts/MM/whoever knock the price down far enough it will become a deal that is too good to resist and I'll sell the other and buy more $TSLA. But, for me, they'll have to reach for a nice big discount and I'm not really expecting it. (It helps that this is in an IRA so I don't have to worry about taxes on short term trades.)
In short, trying to time the market is foolish: if you want $TSLA buy $TSLA. Being flexible with your assets is fine, but keep in your mind that holding it as cash is an implicit belief that doing so will provide higher returns -- but your post seems to lack conviction in that regard.