Merckx was called The Cannibal because he left nothing for anyone else to win. There is a replica jersey that combines all three winning categories (yellow, green and polka dot) although I don't know if Merckx ever wore one.
Wiggers is almost over the hill in cycling terms; 32 is old, although if he were really committed (and had the same team, which probably ain't going to happen) he might make three wins and equal LeMond*. The peak age is about 29 for a grand Tour.
Froome could have five in him but he needs to work on his TT. Nearly all recent winners, and quite a few older ones, won it by also winning the TTs. There is just too much time at stake.
*the 1986 Tour, when he battled with Hinault, was what Froome could do to Wiggers next year if they're both still with Sky.
BTW, Wiggers' time today wouldn't have been shameful for a "25"...but it was a "35".