I did some number work on the EK/BS multi-class possibilities, specifically where DPR and and the new cantrips are concerned... you can find it in the other wizard thread here:
http://www.enworld.org/forum/showth...o-Wizards-5e&p=6818344&viewfull=1#post6818344
tl;dr
Pure EK, Pure BS, and BS with a 1 lvl fighter dip all seem more viable than EK with a BS dip.
My personal favorite is Fighter 1 / BS X (assuming your DM lets human BS [for dual wielder]), which I'm currently playing out in my groups campaign. The DPR isn't far off pure EK, but with full spellcasting.
I've been thinking about sentinel a lot for this character. The benefits with the play style are obvious. However, I think the choice isn't as obvious. A BS only has five ASI's, four if you take a 2 lvl dip (which you might for action surge). You need four ASI's to max out Dex and Int. I think Warcaster is a must with any melee BS build, it just synergizes so well. Sentinel on the other hand, is more situational, and I think we can agree even as a BS, the wizard isn't going to be making as many OA's as the BSF. The effects of Booming Blade (usable as an OA with Warcaster) also duplicate some of the sentinel concepts. Even a Human BS I think would be better off using the extra feat for Dual Wielder, dipping Fighter for the fighting style, and using his ASI's for Dex, Int, and Warcaster.
Where Sentinel might work best I think, is on a party member in combo with your BS (sadly, I haven't been able to test this yet). I made a post in the forums a while ago presenting a Minotaur Battle Master focussed on ridiculous lockdown:
http://www.enworld.org/forum/showthread.php?473074-Minotaur-Sentinel-Awesomeness
My concept was to have a BS striking at the enemies locked down around the minotaur, abusing static damage spells and forced movement. The BS and/or the minotaur could probably benefit from three levels in Swashbuckler in this combo, but I haven't thought the whole thing through yet. Might try to get the combo running someday if I have the opportunity.