It's pretty highly speculated that Kangaskhan was meant to be a Marowak evolution in the first place, so I could definitely see those two lines being connected someday.
That being said, I'm surprised they didn't go with past-gen evos in Black and White, especially since there were some opportunities. I'm not extremely familiar with all of the Gen 5 Pokemon yet (hell, there are some Gen 4's and even a couple Gen 3's that I'm not entirely familiar with by name), but I definitely see some in there that could work as evolutions of Tauros and Luvdisc, and a pre-evo of Stantler, among others.
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