It might be some some readers interest to see the games. Also, It appers that Gashimov defeated Ivanchuk when Ivanchuk played Bg5 Bb5 system.

I assume that most or the top players won't use their preferred repertoire in a blitz tourn. They save their sharpest weapons for more important games. (Especially given the fact that these blitz games are recorded and published.)

Seems like Kasparov did not advice him to not play Dragon, at least not accelerated Dragon where white can not enter the Bind. This is a blitz game so both players did not play the most accurate moves and I assume Carlsen lost on time since Rykba shows that the final position is a draw. Both players are well known Dragon players.

[Event "World Blitz"]
[Site "Moscow RUS"]
[Date "2009.11.16"]
[Round "3"]
[White "Gashimov, V."]
[Black "Carlsen, M."]
[Result "1-0"]
[ECO "B35"]
[WhiteElo "2758"]
[BlackElo "2801"]
[PlyCount "154"]
[EventDate "2009.11.16"]

1. e4 c5 2. Nc3 Nc6 3. Nf3 g6 {Gashimov is also a leeding Dragon experts so
this game is interesting} 4. d4 cxd4 5. Nxd4 Bg7 6. Be3 Nf6 7. Bc4 O-O 8. Bb3
d6 9. h3 {if this is white most critical variation the Dragon must be in good
shape} Bd7 (9... Na5 {is my preference eg} 10. O-O b6 11. f4 Bb7 12. Qd3 Nxb3
13. axb3 Nd7 {and is unclear how white should continui. Black is at least equal
}) 10. O-O Qa5 11. Re1 {is given question mark in Fritz 12 opening book} (11.
f4 {is mainline in Fritz 12 opening book nad statistic are cleary in white
favor while Rykba calls it pretty equal}) 11... Rfe8 (11... Rfc8 12. Qd2 Ne5 {
equal}) 12. Qe2 Rac8 13. Rad1 Nxd4 14. Bxd4 Bc6 15. Nd5 Nd7 (15... Bxd5 {is
sinply good for white} 16. exd5) 16. Bxg7 Kxg7 17. Qe3 Nc5 (17... Qc5 {is a
Rybka 3 idea since queen exchange favors black in this position}) 18. Qd4+ e5
19. Qe3 Nxb3 20. axb3 Bxd5 21. Rxd5 Qa2 (21... Rc5 {is given as best move by
Rybka 3} 22. Rd2 (22. Rxd6 Rxc2) 22... Rc6 23. c4 (23. c3 Qb6 24. Qxb6 Rxb6 25.
b4 Kf6 26. g3 Ke6 27. f4 Ra6 {gives white a symbolic advantage}) 23... Qb4 24.
Red1 Re6 25. Rd3 (25. Rd5 a6 26. f3 Rb6 27. R1d3 h6) 25... a6 26. Rc3 Rf6) 22.
Qc1 (22. c4 Qxb2 23. Rxd6 {white is better}) 22... Rc6 23. b4 b6 24. c3 a5 25.
b5 Rc5 26. Red1 Qc4 (26... Rxd5 {is Rybka 3 suggestion} 27. Rxd5 Rd8 {and
white can not make progress}) 27. Rxd6 Rxb5 28. Qg5 Rc5 {loses by force} (28...
Re6 29. Rd7 Rf6 {and white can not make any progress}) 29. Qf6+ Kg8 30. Rd8 Rc8
31. Rxe8+ Rxe8 32. Qxb6 Qxe4 33. Qxa5 Qc2 34. Qa1 Kg7 35. b4 Rc8 36. Rc1 Qb3
37. c4 Qxb4 38. Qxe5+ Kg8 39. c5 Qb5 40. Qd5 Kg7 41. Qd6 Qc6 42. Qd4+ Kg8 43.
h4 h5 44. Kh2 Qc7+ 45. g3 Qc6 46. Rc3 Re8 47. Re3 Rc8 48. Re5 Qc7 49. Rd5 Re8
50. Rd6 Rc8 51. c6 Qa5 52. Qf6 Qf5 53. Rd8+ Rxd8 54. Qxd8+ Kh7 55. Qd4 Qc2 56.
Qf6 Qc4 57. Qd6 Qc2 58. Kg1 Qb1+ 59. Kh2 Qc2 60. Qf6 Qc4 61. Kg2 Qd5+ 62. Qf3
Qc4 63. Kg1 Qc1+ 64. Kh2 Qc4 65. Qf6 Kg8 66. Qd8+ Kg7 67. c7 Qc5 68. Kg2 Qc6+
69. Kf1 (69. f3 {wins}) 69... Qc1+ 70. Ke2 Qc2+ 71. Ke3 Qc3+ 72. Ke4 Qc6+ {I
did not see this game live but I assume Carlsen lost on time here. According
to Rybka 3 the position is a draw!} 73. Ke5 (73. Kf4 Qc1+ 74. Kf3 Qc6+ 75. Ke2
Qc4+) (73. Ke3 Qc3+ 74. Ke2 Qc2+ 75. Ke3 Qc3+) (73. Qd5 Qc2+ 74. Kf3 Qxc7)
73... Qc5+ 74. Kf4 Qc4+ 75. Kf3 Qc6+ 76. Ke3 Qc3+ 77. Kf4 Qc4+ 1-0

I do not think Carlsen will switch openings. Not shure what he prefeces these days but unless I missread Carlsen has even played Dragons while Kasparov was hes secret trainer.

Kasparov used Dragon as surprise weapon but played mostly Najdorfs.