IMHO, the good sales of GTA V were alrady baked in pre-release. A small part of the bump in the last week may be attributable to the stellar sales (highest grossing entertainment product, etc etc) but the REAL reason for the pop was the revelation that GTA online would feature microtransactions.
It's going to make TTWO a ton of money. I think the stock will start soaring when GTA Online is released and they announce that more hours were spent playing it on opening weekend than were spent building the pyramid of Cheops. When they announce how much money it's making in their next earnings conference, we will have liftoff.
I don't own any right now, but I'm thinking of freeing up some assets to buy here.
Just my two cents on TTWO, the amount of sales that have been announced were not all baked in prerelease; its possible that they might sell their yearly forecast (19M units) in two weeks, or by sometime in october; that's crazy and can't be accounted for in the current price. Heck, have you noticed zynga is worth more than twice what ttwo is valued at? talk about the market not knowing about the VG industry.
The reason the stock price had not moved much was a downgrade to "sector perform" from some unknown "analyst" saying that they have no pipeline (this was just previous to release of gtav, btw.)
AND
The options expiration date last friday the 20th; there were big interests making sure that the stock price ended under $17 dollars, and lo and behold, it ended at 16.99 (market manipulation much?). There was some crazy volatility that week, with the stock surging in the AM and losing all gains by the PM. (Congrats Goldman Sachs)
We pass the options expiration date, and have a nice move upwards last week, and I can see it going steadily for the next few weeks (barring something stupid happening in DC) until a nice pop when earnings are announced at the end of Oct.
$20 is doable by earnings, IMO if washington doesn't have a lasting effect on the whole market, and if there's any type of logic in the market, it could be in the mid twenties by the end of the year or january earning conference. (beware those option expiration dates, though).
Due to the low float of TTWO, the steady good news coming out will probably make the price will go up faster than your usual stock. It hasn't had crazy unjustified gains like many others during the year (gamestop, ea, to a lesser extent TSLA and FB), so I expect it to still keep moving upwards for quite a while longer.
Disclaimer, I am not an analyst (but I should be, I at least know more of the industry than some of the bozos out there). I have been long on ttwo for a couple of years and continue to buy more when I can and hold what I have. At the very least I consider it a steady investment that's undervalued at the moment with a good potential for breakout.
A certain celebrity analyst called GTA online "a stupid idea"...we'll see how those microtransactions do....apparently he wasn't expecting them? Sorry for the long post, but hopefully someone out there learned something; always do your own research when buying stocks!

good luck to all!