Brock IMO was the catalyst to UFC breaking that glass ceiling, Chuck and Randy were pretty big draws if my limited knowledge is correct. They were going to get the spotlight eventually but Brock dragged that spotlight onto them, everyone wanted to see the arrogant wrecking ball meet his maker.
As for an effect, in the short term IMO yes. Brock was their biggest asset, however he brought a lot of new eyes to the product and with the talent the UFC has, a lot have stayed.
An interesting question I'd like to raise is, will the UFC decline in the next 10 - 15 years or even before? Wrestling hit that decline as has boxing bar a few super fights, MMA is a baby sport but has it peaked too soon, leading it to fall to obscurity in a short time?