Galaxy S4 Release Date could be announce in Q4 this year. Samsung Galaxy S4 would have Powerful specs and low price compare to Apple iPhone.
Samsung S3 was released in the end of Q2 and Samsung Galaxy S4 development has been start in Q3 2012 which indicate the activeness of Samsung to this competition world with Apple smartphones.
Imagination: Samsung Galaxy S4 Leaked Images
Every New smartphone comes with new updated Operating System and powerful processor. Samsung also knows that you will have to update your specs to be remain in the competition so in each release Galaxy S series get new design and updated specs.
Galaxy S Series Video
Samsung S4 Specs
To compete with Apple iPhone 6, Samsung will need to include latest 2.0 GHz A15 Quad Core Processor for Galaxy S4 because in the next release, Apple will include A6 Processor to give more power to Siri.
Most Probably, Samsung will use Android 5.0 Jelly Bean in the upcoming Galaxy S4 and include a virtual assistant just like Siri for iPhone. There is an exist app for Android called S-Voice but its not too powerful. With Android 5.0 Jelly Bean, Google and Samsung will try to make S-Voice more powerful and include more operation to S-Voice controls.
S-Voice assistant could be the main advantage and power for Android 5.0 which could be used in Samsung Galaxy S4 while Apple will also be behind in this competition, iPhone 6 could get iOS 7 and A7 Processor to compete with Samsung, Motorola and other smartphone brands.
Running, S3 runs on Android 4.03 Ice Cream Sandwich while Android v4.0.4 Ice Cream Sandwich has just released. It looks like Android 5.0 Jelly Bean update will come up at the end of this year and most probably, Samsung might use it in Galaxy S4 development.
Review: New Galaxy S4 would have Android 5.0 and A15 2.0 GHz Processor.