Valve is working on the latest iteration of Counter-Strike!

Over the weekend many CS:Source players were invited to the Valve headquarters. Apparently the new CS: Global Operations will replace CS:S's spot!

The gameplay will be closer to CS:S than anything. Some maps the testers have seen include well known dust, aztec, inferno, nuke and train.

Update: Valve officially announced Counter-Strike: Global Offensive.

Source: Official announcement, CS: GO Steam page
Links: SK, ESEA, cadred, Reddit thread