As long as you do not have a gap of 63 days between your COBRA ending and your next plan starting, your new plan will cover your pre-existing conditions in 2013. In 2014, all plans have to cover pre-existing conditions but you have to enroll during open enrollment. (You can enroll in mid-year if you have a family status change.)
Medicare will also cover your pre-existing conditions, however, no matter how long you were previously uninsured. Make sure you get your paperwork started to enroll in Medicare on time. You can visit medicare.gov to get information about enrolling.