I don't know that they'll seem dated really, but of the names that are still somewhat popular right now, I think it'll seem too late to name a baby
Madison,
Savannah,
Aubrey,
Mason,
Chase,
Wyatt.
Dated, to me, means something like "sounds very likely to be over the age of 40" .. a bit different from just being out of fashion as a baby name.
In 20 years probably
Ashley,
Taylor,
Dylan,
Madison,
Katelyn /
Caitlin etc,
Mackenzie,
Alexis,
Tyler,
Joshua,
Justin,
Zachary will seem dated in the way that names like
Crystal,
Michelle,
Kimberly,
Kelly,
Tiffany,
Brian,
Jeffrey,
Kevin do right now.
- mirfak