There was a time when phone size was the defining characteristic of cool: the smaller and slimmer, the better. Then came the smartphone with touchscreen, ushered in by Apple's iPhone, with a tiny 3.5-inch display, which was just fine at the time. But gradually, phone users began demanding bigger and bigger screens. Apple stuck doggedly to the 3.5-inch format through several generations, eventually allowing a 4-inch display in its fifth generation.Meanwhile, Samsung had invented the large phablet format with its Note series, and the world was bypassing Apple.Finally, about 18 months ago, Apple gave in, delivering the iPhone 6 and 6 Plus with 4.7-inch and 5.5-inch screens.story_article_left1This war of formats was largely of interest to the high-end of the market, where high-income earners could afford fat monthly contracts or enjoyed company allowances that gave them a choice of any device.Now history is beginning to repeat itself in the entry-level market. Just two years ago, the first 3.5-inch phones costing under R550 arrived in South Africa. Huawei cleaned up with its Y220 model, followed closely by the Vodacom Smart Kicka and the Alcatel OneTouch Pixi. These devices were responsible for the smartphone truly going mass-market.Not entirely coincidentally, the Kicka was also manufactured by Alcatel, under contract to Vodacom, and Vodacom also carried its own branded versions of the Pixi. Its successor, the Pixi 2, was another massive seller.So, while Huawei opened up the entry level, Alcatel became the dominant provider, selling around six million smartphones in South Africa in three years.A quarter of those carried the Alcatel name.It can therefore be argued that Alcatel currently sets the direction for the entry level, in the same way Apple and Samsung have led the high end. So, it is highly significant that its most recent flagship in the entry-level range, the Pixi 3, has a 4.5-inch display.At the annual Mobile World Congress starting in Barcelona tomorrow, most attention will be on launches of major new flagship devices by Samsung, LG, Huawei, ZTE and Alcatel.But the big shift is happening elsewhere."Eventually 3.5-inch will be phased out," says Ernst Whittman, southern Africa country manager at Alcatel OneTouch. "We still have the 3.5-inch model in the portfolio, but eventually 3.5-inch will die."story_article_right2Bigger screens normally mean shorter battery life, and 4.5-inch screens have not yet changed that rule. Still, the Pixi 3 offers a respectable 10 hours of talktime. It is also pre-loaded with social and chat apps such as WhatsApp and Viber.These apps appeal most to entry-level users, since they save massively on the cost of messages and calls.With bigger screens, users can start turning handsets into tools of productivity. This potential will increase as the default size of displays rise. And it won't stop at 4.5-inch. Just as 4.5 is supplanting 3.5, soon 5-inch will be the new 4.5."I'm not sure of the longevity of the 4.5-inch format, because we are seeing rapid cost reductions of the display panels," says Whittman. He compares the price shift to the trend in SD memory card pricing, where a card with 2GB capacity now costs more than a 4GB capacity."We think the 4.5-inch format has a good two years to go at the entry level, but with the cost of 5-inch panels dropping, there is going to be a breaking point where 5-inch becomes the new default."Goldstuck is the founder of World Wide Worx and editor-in-chief of Gadget.co.za. Follow him on Twitter and Instagram @art2gee..