For example, Spain-based international mobile operator Telefonica recently introduced its own IP messaging service that does much the same things as RCS, Sharma said. Telefonica also offers RCS. Many of the world's major carriers have endorsed RCS, but it's not clear yet how much or how quickly they will truly embrace the technology, he said.

"How fast RCS can actually gain subscriber base, and whether it can effectively compete from a pure market reach perspective, I think remains to be seen," Sharma said. It won't happen in the next year or two, he said. For now, "there's just no competition with the existing IP messaging guys." New features and intelligent pricing could help RCS to gain more ground, Sharma said.

Though carriers can offer both RCS and their own IP messaging services, a key success factor will be how many other people a subscriber can reach with a given software suite. For example, Apple's Facetime video calling system may be popular among iPhone and iPad users, but its success has a limit as long as it's not available on other vendors' devices. The same effect could hamper RCS if it's not used or offered widely enough, he said.

The iPhone may represent one of the major stumbling blocks for RCS, said Peter Jarich, an analyst at Current Analysis. Apple hasn't embraced RCS, and there are many third-party apps offering similar capabilities for its wildly popular phones. Without Apple, "you've just lost a huge chunk of the market," Jarich said.

The IDG News Service