Let me address some of the obvious potential impairments. I am aging this beer in a corny keg so I know oxygen exposure is highly limited. I've tried letting it ride for a few months with the posts unscrewed to help out improve oxygen but still not even a thin pellicle formed. I've opened the lid many times over the course of the seven months it's been aging. Maybe it's still not enough oxygen to get serious sourness but on the other hand I would expect to see at least some brett activity in the flavor. None so far. I know people often comment that corny kegs rarely make for sufficiently sour beers but zero sourness or funk shouldn't be the case.
I am doubtful a lack of food is an issue. The gravity also isn't so low that the beer is completely dried out. I've checked it with my refractometer and the strain I used for primary fermentation is known for leaving beers under-attenuated, so it was a perfect starting point for a sour beer. It's also a highly expressive Belgian strain so again I would expect some brett manipulation of the esters even if brett couldn't find any sugars to munch on. Still, I will probably add a little simple sugar and maltodextrin in the near future to add a little extra food to restock it just in case.
My suspicion is that the volume of viable brett and bacteria in the dregs was too little for five gallons of beer. My solution is going to be adding more dregs as I clear out sour beers. I've already dumped in the dregs from one of my lambics and I have a few sour beers in the house that will help this beer along. In particular I have a lonely bottle of Jolly Pumpkin I smuggled into Texas from Colorado that I expect will go a long way towards helping this beer out since JP dregs are known to house quite the voracious organisms.
I wouldn't mind bottling the beer as is and moving on except the strain I used, due to it's under-attentuative nature, makes for a very syrupy beer. I really dislike syrupy Belgian beers. The ester profile is like a blend of Chimay and Duvel, which is quite tasty, but the yeast lacks the dryness those strains reach. (This is yeast I cultured from a bottle of South Austin Brewing Golden Ale.) I don't have a need for the corny keg for the foreseeable future so I'm in no rush to do something with the beer, I would just like for it to do something.
I'd like to play around with this beer once it sours. I'll probably bottle some straight but I'd also like to hit some with some wine or liquor to give it a barrel-aged-like flavor to go along with the oak I already added to it. I'd also like to play with dry hopping some and maybe add some fruit to a portion. I plan on trying to use the slurry from this beer to create sort of a house culture of funk/sour that I can add from beer to beer for souring. Given the unwillingness of this beer to get sour I may be waiting a while before any of that happens.