Speaking with MTV, EA have taken the unusual step (at least for them) in assuring Burnout Paradise players that future DLC for the title won't split the online community between those who opt to buy the DLC and those who don't. Issuing a written statement, they explain:
It's our intention to extend the life of Burnout with additional DLC in the near future. As mentioned, we don't want to split the online community between those that have content and those that don't. Our intention is to offer both free and paid for DLC in a way that enables everyone to 'see' the content, even if they have not paid for it.
They wouldn't elaborate on what exactly that meant. Which means I'm just going to speculate that they'll open up new areas of the map for you to drive around, but unless you pay for the DLC, you won't be able to trigger any of the events contained within.
EA Says You'll Experience 'Burnout Paradise' DLC -- Even if You Don't Buy it [MTV]