No, the Chromium developers have made it clear that they will not support multiple omnibox keywords for extensions:
My take on this is that an omnibox keyword is a UI surface, like a page/browser action. We limit extensions to 1 UI surface to avoid adding clutter. Given that, I don't think we should implement this.
Granted, this bug asks for both the ability to define multiple keywords and dynamically change those keywords on the fly. However, the developer response seems opposed to multiple keywords in general.
The same response suggests an alternative:
The keyword is meant to act as a prefix for your extension, so rather than having N keywords, how about 1 keyword that accepts N commands?
Instead of supporting both keyword1 something
and keyword2 something
, you can use masterkeyword keyword1 something
and masterkeyword keyword2 something
.