is the big al replacing the bongo as the instrument most easy to criticize ernie ball's design team over? yes
If by criticizing, you mean criticizing the design team for being too awesome, then I agree with you.
I have one of each and I love them. The Bongo is still one of the best feeling basses to have in my hands. The Big Al plays great, looks unique and has an incredible variety of sounds. I've never been much for tradition, in fact part of the reason I sold the second Big Al I had was because it was Sunburst, but I digress. Musicman doesn't seem to be thinking about killing anything at the moment. Your Stingrays, Sterlings and Stingray Vs are probably always going to be the majority of their sales (as well as black and natural), but there are people who are captivated by the "oddballs" that probably wouldn't have been buying a new Stingray anytime soon (much like myself).
I'm as big of a Musicman fanboy as anybody, but Stingray and Sterlings while great basses, don't do all that much for me. I really choose my instruments for myself, its nice to have buddies that like my gear as well (and I do have them), but I just wouldn't feel like I was being me if I was gigging a Jazz or P. Or as it says under my avatar:
"Doesn't care what you think, I have good taste"
More relevant though, I just picked up a Single H bongo for the 3rd time last week. Then I saw the Single H Big Al and got a little annoyed for a second since I am such a fan of the bass. However, playing the Single H at practice and thinking things through, they still really do different things. I don't want the extra mid push of the Mahogany, I find 4 band EQ overkill for a single pickup bass, and I like my humbuckers active. Plus, I find the playability of the Bongo to be better than the Big Al (not that the Big Al is bad mind you). If I need a passive sound, I'll take the Big Al (which I play almost exclusively in passive). My band will be recording three songs early next month, I'll take both basses and probably use the Big Al on two and the Bongo on the other.
I know I'm biased and all, but these are pretty awesome looking.
And I know the Big Al will never appeal to everybody lookswise, but I think some of us pull it off quite nicely: