I am not sure if it would spell the end, but it would reduce their influence. It is probably the most common GPL program included in non-GNU/Linux systems.
Truthfully, it is really a bad business decision not to send patches back to the original project. If you can get them adopted, it will save on maintenance (since everyone is maintaining your patch). It seems that companies that won't file patches back under BSD/MIT are not doing themselves any favors. Further, given the decision process at those companies, it is probably better that those patches don't get added to the mainline.