I'm not certain what my point is, but I wanted to mention that jumbo frames don't work over the Internet. More of a LAN thing.
If you want to use jumbo packets on the internet at large, you need to have working path MTU detection, which realistically means at least probing, but you really should have that at 1500 too, because there's still plenty of broken networks out there. My guess is you won't have many connections with an effective mtu above 1500, but you might have some.
I'd be willing to bet my lunch more 10x more places have been moving down to assuming 1280 byte connections (since IPv6 guarantees it) than have been peering on the internet at >1500 (not counting 1504 for VLAN tags and whathaveyou).