Is it enough?... yes.
Should you go 16gb?... yes.
No game will use more than 2-3gb by itself.
But I don't know what your other apps can use. If they are 64 bit enabled, then they usually can use ram to avoid workfile I/O.
Ram is cheap, and a 16gb kit of 2 x 8gb does not cost that much more.
You can then be certain that all your concurrent tasks ill continue to run without interference.
And, windows can keep more code in ram available for instant reuse.
Just because you have money doesn't mean you should throw it away.
Playing battlefield 3, with GIMP and 20 tabs open in Chrome, Windows has never even used 7 of my 8GB. (And I have no pagefile.)
There's NO point in buying 16GB of ram - just get an 8GB kit with decent speed and tight timings.
EDIT: That being said, you'll get lag doing all those things at once, but it won't be because of a lack of RAM - it'll be from rendering, skype, and the game competing for clock cycles on your CPU.