WiFi vs 3G - Discussion Not for India
In US and other countries WiFi networks are available all over the country and people prefer it because 3G services are costly and WiFi is more reliable as it is backed by wired broadband network.
In India Wifi hotspots are rarely available and not really affordable (check out Aircel Wifi tariff).
3G(HSPA/EVDO) services are damn costly at its initial phase and 3G is not available everywhere like 2G networks. So both WiFi and 3G in India are in nascent stage. These also say why tablets or mobiles with Wifi only cannot make good sale.
Tablets - For Whom?
Tablet market in India is booming, and market is crowded with desi and international brands. MNCs already launched their products to India like Apple iPad, Samsung Galaxy Tab, Dell Streak, HTC Flyer, Blackberry Playbook, Motorola Xoom, Acer Iconia Huawei Mediapad etc.
Indian companies also are in the race. Olive launched Olivepad almost 1 year ago. HCL, Spice, Accord, Beetel are also joining or to join the tablet race. Recent additions are Chirag Tango and EAFT MagicTile Marathon tablet. But internationally acclaimed Notion Ink Adam is messed up with its poor manufacturing and marketing strategy.
In spite of the heat from tablet, PC & laptop market remains steady. Because tablets do not have key features like USB ports, CD/DVD drives (it still make sense in India despite presence of pen drives/portable drives/SSD drives), upgrading memory! Tablets are essentially a content consumption device than a content creation device. After PC/laptop and mobile phone tablets are 3rd kind of device, but it does not replace others.
Factors such as spreading broadband access and usage, increased affordability and availability, local contents etc are the main driving force behind tablets.