I get what you're saying, but I'm not that convinced that's how the carmakers think.
What percentage of car owners ever replace their factory head unit? Most of the people I know don't have an aftermarket audio unit; they definitely don't install RSE video units in great numbers.
There are a lot of makers that sell-up their higher-end models by advertising things like Alpine/Monsoon/Whoever speakers & head units, plus satellite radio compatibility. I suspect that they get a non-zero chunk of the satellite and navigation monthly service fee as revenue, too. Over 8 years, that ongoing revenue stream is better than whatever their margin is on a particular head unit. Plus by maintaining good working relationships with the head-unit OEMs, they get year-after-year business on the new models. Ticking them off by locking out 3rd-party upgrades can't be worth that.
Anyway it seems like car makers and head-unit OEMs *are* interested in some standards; that's what MOST is for, and XM/Sirius makes lots of add-on units to retrofit different brands.
The interesting thing to me was when Rudolf Streif said that carmakers are wanting to leverage their IVI systems as "app platforms" like the smartphone market is giddy on. There may not be a ton of possibilities for driver-facing apps (though I'm sure the 4square types are already dreaming up something useless), but rear-seat gaming is sure to garner some sales. Anyway, it almost necessitates a replaceable "IV unit" to upgrade processing power and network standards. That would be a real big change. In any case, the IVI working group already talks about separating vehicle sensors and data from the head unit, connecting them instead on existing bus standards like CAN.
We'll all see who's still impressed with the locked-in, Ford-only nav unit they can get today ... when 2017 rolls around.