I'm basically developing a Game with a background music licensed under the CC BY 3.0 along with couple of other music/sound effects. Now suppose a YouTuber/Gamer in future decides to publish a walk-through video of the game, will he get in trouble for not attributing the Music creator in his/her video if someone reports it?
This is entirely up to the person who owns the copyright on the music (which is nearly always the same person who you are required to attribute). If this person decides to make an issue of it, then they can ask YouTube to take down the video. You have no say in this process.
In most cases, someone who has licensed their work under such a permissive license is more likely to just contact the video creator and ask for attribution in the description (which is a standard form of attribution on YouTube). However, there have been reports of copyright trolls uploading material under permissive licenses, and then finding and suing people who make small mistakes in attribution. Cory Doctorow has written about this problem at length.
You should be aware of the differences between versions. Under CC 3.0 licenses, any breach automatically terminates the license:
This License and the rights granted hereunder will terminate automatically upon any breach by You of the terms of this License. Individuals or entities who have received Adaptations or Collections from You under this License, however, will not have their licenses terminated provided such individuals or entities remain in full compliance with those licenses. Sections 1, 2, 5, 6, 7, and 8 will survive any termination of this License.
Under CC 4.0 licenses, the license restores itself automatically if the breach is cured within 30 days of being notified:
a. This Public License applies for the term of the Copyright and Similar Rights licensed here. However, if You fail to comply with this Public License, then Your rights under this Public License terminate automatically.
b. Where Your right to use the Licensed Material has terminated under Section 6(a), it reinstates:
- automatically as of the date the violation is cured, provided it is cured within 30 days of Your discovery of the violation; or
- upon express reinstatement by the Licensor.
For the avoidance of doubt, this Section 6(b) does not affect any right the Licensor may have to seek remedies for Your violations of this Public License.
There is no such restoration term in 3.0, so in theory, once you violate a 3.0 license, you have to ask the copyright holder to give you a new license, and they can refuse. In either case, the copyright holder has the right to sue over the violation if they are so inclined, but in the case of 4.0, they can only sue over the past breach, and cannot prohibit ongoing use once the breach is cured.