Well Apple used to release the new iPod generation every September, however this time rumors predict that the iPhone 5 will be released in September. If that is true then Apple most likely wont release both the new iPods and the iPhone at the same time.
Time will tell.
i want to know, if ipod 5 have bigger screen , i want to wait for it , i thought apple will introduce iphone and ipod in june ?
must i wait for ipod 5 or buy ipod 4 . if i want to buy ipod 4 , i will buy it a month later
Nobody knows for sure when Apple will introduce the next iPod or next version of pretty much anything. Apple keeps it all very secret.
More likely a new iPod Touch in September than June. Apple uses the free iPod promotion during the summer to clean inventory before introducing new models.
No one outside of Apple knows if iPod Touch 5 will have a bigger screen or not.