We are past the days of musical acts being iconic in the same vein as the past. The golden age of popular music is long gone. 40 years from now, I highly doubt people will be listening to stuff like Kanye West, Lady Gaga, or Justin Timberlake the same way people today still listen to The Beatles, The Rolling Stones, or Elvis. Music is not held to the same standards today. Its cheap, manufactured, and disposable. Pop, and the most commercially successful genre today, rap/hip hop, is full of "here today, gone tommorow" drivel that people were embarrassed to admit they liked 6 months ago, let alone 40 years from now.
Somehow, I don't think Lil' Wayne will transcend the test of time. Sorry. We are all unfotunate enough to be part of the MP3/digital/short attention span era. We aren't even patient enough to buy a record and listen to the entire thing, what makes anyone think we are building icons?