I think all the earned transaction fees(well excluding the costs of running the node) will go back to the BTS X development fund. Shareholders will vote for what is the most profitable for their investments. Whoever promises to give back the most transaction fees will get the most votes.

If BTS X reaches the point where $100 million in transaction fees are accrued yearly and $1 million is distributed to each delegate, then how will the delegate be likely to use his or her dividends?

1- Marketing his or her reputation? 

2 - Technological upgrades for the network?

3 - Funding for start-up DACs & Marketing promotions for ancillary DACs?

4 - Salaries / Bonuses?

5 - Charitable donations?