The tandem track pairs (and articulation) is used in the Swedish BV-206 variants, or M973A2 used by the US Army. This is of course NOT a MBT, but a 7.5 Ton lightly armored tracked vehicle. One problem (for tanks) with the articulation would be the inability to do a pivot turn
Aparently quad-tracked tanks will be de rigeur in the 26th century, at least according to the makers of Halo 2.
My guess is that all of these tanks are still succeptible to top attack munitions.