Users on Twitter can expect the type of ads they'll be seeing in their timelines to get more precise in the future with what the folks from Twitter are calling "keyword targeting in timelines." What this means is they'll be targeting words in your timeline or things you tweet, and delivering ads based on those keywords.
It sounds like ads are about to get much more targeted and direct for each individual, whether they like it or not. Now advertisers will be able to offer and place promoted tweets in timelines with much more focus on the subject matter to each person tweeting. If you mention something you like such as Doritos, or the NFL, you'll likely get some targeted ads based on those keywords.
Twitter will be allowing context to play a much bigger role in your everyday advertising intake. There is good news here though. That being the amount of advertisements that are popping up shouldn't actually increase for any one, they'll just be more direct and more useful. So it's sort of a win win, we guess.
"Users won’t see any difference in their use of Twitter — we’re not showing ads more frequently in timelines, and users can still dismiss Promoted Tweets they don’t find relevant. In fact, we believe users’ experiences with ads will improve as a result of this feature as they see more relevant Promoted Tweets." - Twitter
According to Twitter and their array of advertisers the feedback and amount of ad engagement has been much better using this new approach in a limited beta lately. Basically, get ready for some better and more relevant promotional tweets.