As a fellow user of Vegas Video, I have no inside information on this, and even if I did, I probably would have signed a Non Disclosure Agreement (NDA) and would not be at liberty to comment. I certainly hope they do provide surround support, and I submitted a feature request requesting support for both stereo matrix Dolby Surround (analog) and Dolby AC-3 5.1 digital surround. You might want to submit a feature request of your own. SoFo personnel read these forums, but the feature request ensures that your request will not "fall through the crack." There is strength in numbers, so it is crucial that a significant number of users are perceived to want support for surround sound. Money talks.
Sonic Foundry has already provided 5.1 encoding in their Soft Encode product, but that has been discontinued for several years, and when it was available it was expensive, at about $1000. I understand that at least one reseller still has a few copies of Soft Encode but, other than the forum here, it has no support from Sonic Foundry. You can't even download a PDF manual.
Dolby Labs charges to license their patented encoding technology, so that prevents a Dolby encoder from being extremely affordable. I don't know if Dolby's charges are levied on a per-software-box basis, or on a per-product basis, or what. If the latter, by selling a lot of a product the cost to the consumer could be made more reasonable. Hopefully Sonic Foundry can negotiate a favorable deal with Dolby Labs on a future surround sound product.
In the meantime, there are some other companies that do provide surround support. Our friends who use Apple products can feel pretty smug about this, because a plug-in for Final Cut Pro 3 provides surround support. They can author 5.1 DVDs today. And there are some third party DirectX Audio plugins that provide limited surround support. I plan to experiment with what I can do with what is available (and affordable) today. Be aware that Sonic Foundry personnel may not be at liberty to discuss their company's future business plans in any detail.