yea thats a good question if this money will be "enough"... Theoretically it could be enough if steem / steem dollar will be used as a currency, or even if steem manages to get a similar value to facebook.
Currently steemit allows to advertise / promote posts, but this promoted posts are not very visible yet.
I would suggest to switch to the following display:
On the first page, the posts should be chosen according of the votes they got in the last X days. 20 % could be chosen from the promoted posts, these could be marked like for example google does with advertisement.

The problem i see currently is, that one of steems main goals is to reward content providers without the use of advertisements that hinder the users experience.

Second, steem is open source, so in theory everybody could create their own display without advertisement.
I think later could be fixed through changing the license, but i guess this would make big part of the current community angry, because steems focus was first of all to reward content without using advertisement.