Introduction:

Verizon is the largest CDMA carrier in the United States. Data on the CDMA side of things typically follows the Qualcomm provided solutions (i.e. EVDO rev 0, A, B, C etc.) Verizon recently announced they plan to use LTE instead. LTE is associated with the fourth generation data standard for GSM users. When this occurs, we should see compatible roaming (at least for data) between Verizon and GSM carriers. Don't get too excited yet, as the plan states in the next three to four years. Lots of things change in three to four years especially with technology.

Speculation: We already see folks placing voice calls over data networks using VOIP technology. In some cases via Skype, and in a different sense for push to talk implementations. It's not hard to imagine devices which automatically route both voice and data over this data connection. If LTE brings widespread roaming opportunities world-wide, and folks use it for voice too, then you have some very widespread compatibility not currently available to CDMA users. If true, this would apply significant pressure to existing CDMA carriers, and perhaps lead to a global standard (which already exists in the form of GSM but doesn't include a large number of CDMA customers mostly in the US).

Notes: I'm no expert on these technologies, and I may not be fully be understanding their implications, but what I've stated above may be much less "science fiction" and more of a reality as time passes. It just makes sense to maximize one's possible customer base...

Further Reaching: If a global standard takes hold in the US as it has elsewhere, you'll see cellular service become more of a commodity. In some ways this will benefit consumers (as your phone would work more universally) but it may also lead to consolidation, fewer choices of carrier, and higher prices. Time will tell.