After Chase takes full control of WaMu credit-card accounts in March, WaMu cardholders who also have Chase cards will be able to combine their limits, according to sources with knowledge of the situation. I was able to confirm this with several customer-service representatives at Chase. Additionally, I've also confirmed that WaMu cardholders, who don't have a Chase card, will be able to convert their WaMu cards into other Chase cards.
The only catch, according to one source, is that one of the credit cards cannot have a balance on it. Thus, if you have a Chase Freedom card, with a balance, and a WaMu Platinum MasterCard with no balance, you'll be able to move your WaMu credit limit over to your preexisting Chase card.
A hypothetical situation would look like this: You have a $10,000 limit WaMu card with no balance. You also have a Chase card with a $15,000 limit. If your WaMu card doesn't have a balance, you can move the WaMu limit over to your Chase card, which would turn into a $25,000 Chase card. At that point, you would close your WaMu card, which would leave you with a single card. If there were balances on both cards, a combination would not be allowed.
Update: as of March 9, 2009, you can now combine and convert your old WaMu cards. See the story here (link).
In addition to the credit-limit combinations, WaMu cardholders who do not have preexisting Chase cards will be able to convert their WaMu cards into a Chase card. For example, if you have a WaMu Platinum card (or an ESPN card) you'd be able to convert it into a Chase Freedom card. All WaMu cards that are brought into the Chase fold will be eligible for consolidation and conversion.
After a number of recent setbacks (FICO being discontinued -- link here -- and WaMu's secured card getting the ax, link here), this is good news. Many WaMu customers worried that they'd be treated like second-class citizens once their WaMu cards were transitioned over to Chase. Since customers will be able to combine their cards, WaMu customers won't have to worry about being treated like orphans.
It's expected that cardholders will be able to start combining and converting their WaMu cards as soon as March 9, 2009.