As far as I know, the opening of new betting exchanges is an unpromising undertaking, as even the No. 1 in this business (Betfair) still has problems with the liquidity of many markets.
The main problem is traffic. No Peer to Peer site is going to have the traffic like on a normal sportsbetting site. Its because the site with its own bank roll can offer more bets/odds. Where as in a peer-to-peer system you need to find someone willing to take your bet. Apart from that, you will also need all those people on that one site. There are already a few like wagerr, who even launched their own site and integrated the whole system in their wallet, but literally have no volume from last I visited.
Old fashioned gambling house offers more odds as gamblers continue to choose this type of business against peer-to-peer ystem, though it's existing but more gamblers continue to support and play with what they've fully understand.
Reputable casinos continue to dominate this business as they already win the hearts of more gamblers.
Though there are some who still taking the risk using new system, but the vast majorities still with the old system of gambling.
There might be a push for a more decentralized system like Wagerr in the future, once people support decentralization more and more. Right now its all capitalism. We need a gambling system which is not relying on a website to hold funds, but only as a way to interact with an on chain gambling system. That will solve all the trust issue, and more and more bigger bankrolled companies can then offer gambling lines like the big websites. The people setting up those lines can be small companies who have capital and want to be the bank. I don't see why that is a distant future, because it isn't too hard to implement with the current blockchain technology we have.