HTC has just announced a new line of 4G smartphones — the ThunderBolt will come out on Verizon, the Evo Shift on Sprint and the Inspire on AT&T.

With these new arrivals, HTC’s portfolio of 4G devices has grown to six total, including the original Evo, the G2 and the MyTouch.

We were lucky enough to grab side-by-side pics of all three devices at CES today.

The Evo Shift, HTC’s newest Sprint device, features a slide-out QWERTY keyboard, a 5MP rear-facing camera and a low $149 price point that’s sure to attract would-be first-time smartphone buyers. The device has a relatively small, 3.6-inch display and no front-facing camera.

The HTC/Verizon ThunderBolt comes with deeply integrated Skype () technology and is part of Verizon’s all-new 4G LTE connectivity plans. This device also features an 8MP camera and a 4.3-inch display.

The Inspire, which HTC is partnering with AT&T to bring to market, features a large, 4.3-inch screen, as well as some new advances in HTC’s Sense technology, including an online component that will allow users to locate lost phones or wipe a phone’s data from a website.

All three devices will ship with Android () 2.2, a.k.a. Froyo; however, release dates for all phones aren’t yet available.

AT&T has detailed its plans for 4G as well as a number of new devices that will be available on the mobile broadband network by the middle of 2011.

Speaking at CES in Las Vegas, the president and CEO of AT&T Mobility and Consumer Markets, Ralph de la Vega, said the company will have at least 20 devices on the market by the end of the year that can utilize 4G speeds (both HSPA+ and LTE, with the former already deployed to “virtually 100% of network” and the latter due for completion in 2013).

Those devices include three Android ()-based smartphones: the Motorola Atrix 4G, HTC Inspire 4G and Samsung Infuse 4G (which is billed as the thinnest Android smartphone to date). The company also says two 4G-enabled tablets will hit the market in 2011, as well as modems and hotspot devices.

There was no explicit mention of a 4G iPhone, but de la Vega did include Apple as a manufacturer that plans to offer 4G devices on AT&T’s network. Whether that means a new iPhone, iPad or some unforeseen device, that’s good news for AT&T, as recent reports indicate a Verizon iPhone is imminent. That said, the latest indications are that such a device may not yet be 4G capable if and when it hits.

AT&T, which bills its mobile broadband network as the fastest, is the last of the big four U.S. carriers to announce its 4G plans. Sprint debuted its first device – the HTC EVO – last June, while Verizon and T-Mobile have recently launched their own faster networks.