Following last week's launch of Apple's latest iPhone, the iPhone 3G S, the rumour mills are buzzing with speculation about what the secretive company is planning for its next handset.
The biggest possible change could be in the screen. The iPhone's screen has been praised since Apple launched the phone in 2007.
But at 480x360 pixels the screen has remained the same while the rest of the mobile phone industry has moved forward. Today, the Nokia N97 offers a higher 640x360 resolution on a similar-sized 3.5in display, while HTC's Touch HD and Toshiba's Japan-only T-01A both have 800x480 resolution on screens that are 3.8in and 4.1in respectively.
Apple might not want to increase the screen size if it means making the iPhone larger but it's a good bet that a higher resolution display is set for the next model.
No phone maker obsesses as much about aesthetics as Apple, so the company will almost certainly consider an OLED (organic LED) screen. OLED is a fundamentally different technology from the LCD screens used in most mobile phones and offers a noticeably brighter and more vivid display - but it comes with a catch.
OLED technology is still relatively new and it becomes more difficult to mass-produce as the screen size gets bigger. While smaller 2in-class OLED screens are already finding their way into products, Apple won't want to use OLED unless it can be assured of a steady supply of screens that are free of defects, offer a long life and are not significantly more expensive than prevailing LCDs.
Some upgrades are almost assured, such as a faster processor and more memory, although Apple might choose to add a graphics processor. A GPU like nVidia's Tegra chip, used in the new Zune HD, would enable higher resolution and smoother video playback, including high-definition: possibly the iPhone HD?
Away from the screen, Apple could also look at the camera.
The iPhone 3G S brought in a higher-resolution 3Mp camera, but those are already becoming commonplace. Some competing phones, such as the Touch HD and Samsung's Omnia, offer a 5Mp camera today, and this will become more common as time goes by.
Data transmission speeds are also likely to increase to keep pace with mobile networks. The current iPhone and most competitors support downloads at speeds of up to 7.2Mbps over HSDPA networks but many carriers are already planning speed jumps within the next 12 months to 14Mbps and beyond.
A slightly more remote possibility would be the addition of WiMax to complement the Wi-Fi already in the phone. WiMax carriers are beginning to launch service in several cities around the world that offer speeds faster than mobile networks, although the most important determining factor for WiMax would probably be dictated by Apple's business relationships with mobile carriers.
So when can we expect a new model? Apple has used the middle of the year for iPhone launches so if previous timing is taken as a guide look for it a year from now in June 2010.