That was my long-term plan as well. Although I knew I couldn't afford the 24-70 and 70-200 anywhere near the same time, so I opted for the 24-105 and I'll get a 70-200 later. Then I'll probably sell the 24-105 and get the 24-70.
I saw an older 28-70 f2.8L on B&H's used site for a tad over $800. Just FYI in case you want to save $700 in lieu of a few mm of coverage. The 28-70 f2.8L is still a highly regarded lens and this one is rated a 9, which is practically new.