Why do you assume marks will still be present at all?
At some point in time in Wrath (some of the last patches) marks were removed completely and only honor left as currency, somehow I suspect they will apply that right from the start.
I asked Brian about this on Twitter. At first i thought that honor/marks were reset during TBC->WOTLK back then.
They planned to reset honor/marks back then but they didn’t. (Google “honor wotlk reset 2008”)
Brian answered that they plan to do what happened back then. So, no honor / mark reset but arena points reset.
Can’t tell about marks because they were supposed to be removed in 3.3.5 but we’ll probably keep honor. If we can also keep marks to and turn them for 200 honor each it mean we’ll be able to stack up to 75k+74k honor.