WoW: Classic is scheduled for August 27 (technically August 26 if you're in the Americas). The soonest that you can play it is starting in May, during Blizzard's scheduled stress tests. To opt-in you must have an active subscription on your Battle.net account. If you do, go to Account Management and select the Wow Classic beta. Keep in mind, there will be level caps during the test. The schedule is as follows:
Rogue combo points posed another challenge, because the game’s modern resource system knows how to gain and spend combo points, but not how to lose them when changing targets. There are also the older combat formulas to consider, so we had to bring back the code for the prior combat formulas including critical hits and crushing blows. Their chance to occur is also modified by the difference between the defender’s defense and the attacker’s weapon skill. Yes—weapon skill is back. We had the data for this aspect of the classic game, but we also needed to restore the code that increased your skills when you used them and made your skill level affect your chance to hit or get a glancing blow.