Omicrons will not come from cantina. I don't even know how many omegas I've got from cantina nodes because they're so rare that it's counterproductive to expect them and be disappointed, cantina is for shards and signals. I can't imagine omicrons will drop more frequently than omegas.
You get 2 omicrons from the 8th box up in GCs, which actually surprised me, I was expecting them to be limited to the red box only. I wouldn't put it past CG to "adjust" the rewards for GCs in the future to make omicrons more scarce, but for now, you can reliably get 4/week, so 16 a month. You can have enough mats for 2 of new Boba's abilities by the time first unlocks happen in 3 months.
Depending on how often new toons receive omicron abilities, getting mats for 1 omicron ability every 5 weeks is actually rather fair imo. I'll take the good changes where I can get them.