If you're a Verizon customer, you might want to hold off on buying an iPhone 5 according to one analyst.

In a note to investors, Hudson Square Research analyst Todd Rethemeier said he believes the next-generation iPhone will have 4G for only one of the major American carriers. He says AT&T's version of iPhone 5 will come with 4G compatibility whereas Verizon's will not. He said this is because he doesn't think the phone will be LTE compatible, which is Verzon's 4G network. AT&T's 4G network is an advanced version of its HSPA+ network.

For AT&T iPhone 5 users, this could mean download speeds of 5-10 Mbps, compared to less than 1 Mbps for a Verizon user, Rethemeier said.

Rethemeier says if this turns out to be true, AT&T will hold a distinct marketing advantage over Verizon. Not surprisingly Rethemeier recommends people hold on the AT&T stock and sell the Verizon one. Even if Verizon eventually gets the iPhone to run on its LTE network, it wouldn't make a difference he says.

Certainly, when an LTE iPhone is introduced AT&T would lose some of its marketing advantage. However, even when that happens, the phone will be backwards compatible, so the AT&T iPhone 6 would be able to roam onto the HSPA+ network when an LTE network is not available, giving AT&T an advantage in suburban and rural areas for several more years, we believe, Rethemeier said.

Rethemeier disagrees with other analysts when it comes to the topic of whether the next-generation iPhone will be an iPhone 5 or an iPhone 4S. Jefferies & Co. analyst Peter Misek says because Apple is not introducing the next generation iPhone at the WWDC, like the company has usually done in the past, he does not expect it to be a major upgrade.

We believe the likelihood of the iPhone 5 launch in September including LTE [Long-Term Evolution] is now remote, Misek said. According to our industry checks, the device should be called iPhone 4S and include minor cosmetic changes, better cameras, A5 dual-core processor and HSPA+ [EvolvedHigh-Speed Packet Access] support.

Misek also makes a somewhat shocking prediction: Apple will launch an iPhone for both T-Mobile and Sprint in time for the holidays. He also predicts the company will release a cheaper, mid-market iPhone in addition to the other phones. He says the company would still be able to maintain its high margins, even if they floor out at 35 percent. The company's current gross margins are 41.4 percent.