DRDO has been straining at its leash for developing a follow on to INSAS rifle from atleast 2005 onwards. They got the go ahead, or rather I believe the GSQRs around 2009-2010. The first bench test at DRDO labs was supposed to be in Middle of 2012, so we are pretty early in the trials, which can run for many many years followed by delays in setting up the production line.
The info about new MCIWS is very limited, a few short lines in a blog and couple of low resolution picture. But my observations are:-
1. It is supposed to be machined from aluminum alloys which means that it will be light and will not heat up quickly. Even though DRDO has exposure to Composites with MSMG, they have done well to avoid the fad, as plastics tend to distort in extreme climates and weight saving is reduced as some portions have to be backed up by metal sheet in any case. The same philosophy has been adopted by HK-416 which has won the competition for US IAR.
2. Similar to HK-416 we have collapsible butt but DRDO has again done well to avoid additional complexity of hinged butt. The heavy lever in the open butt indicates that the butt contact points for extension and collapse would be true without flex & rattle. The collapsible butt should allow adjustment for ease of carriage, ergonomics, bullet proof jacket and also for confined spaces.
3. Similar to HK-416 design we have straight line design which allows for better control ability of recoil and in auto fire by reducing muzzle climb.
4. Now how multi caliber change is achieved ? seems to be unclear but careful look at the pictures indicates there is rectangle (joint) above the magazine well. This would indicate (my guess) that the rifle breaks open by removing the lower front half of the receiver including the magazine well.
5. First this has the big benefit of removing the hinged upper receiver of the INSAS which has been a big problem. As evident if the sights are mounted on a hinged joint then after some time the joint will become rattly/loose and the sights will not be able to maintain the zero. So similar to HK-416 concept (borrowed from M-16, Sig) the lower part of receiver seems to break open for field stripping the rifle.
6. The Caliber change (my guess) will be evidently achieved by field stripping the rifle, and replacing the barrel & bolt group, lower receiver & magazine well while retaining the butt, trigger group, top receiver, back portion of lower receiver, fore-end heat guards/grips.
7. Personally I think that multi caliber is useless requirement adopted to favor some particular firangi company. Only USA tried adopting it, that for only its SF and even they ultimately walked out of it. Anyway, army has got what they wanted.
8. Most probably the well tested INSAS trigger group, rotary bolt, piston system (borrowed from AK-74 and somewhat same in HK-416), sights etc will be retained. Muzzle break seems to be same as INSAS. Though I hope better alloys will be used to lower weight and improve performance.
9. Army seemed to want a conventional design and thus MCIWS is conventional layout. Again an over-clever design which will allow it to be changed to bullpub or over complicated design like forward ejection + bull pub has been avoided.
10. The gas adjustment system, piston etc are not clear from the pic. Hopefully there is no rapid barrel change which adds useless complexity. (Again there is no rapid barrel change in HK-416 but one can change the barrel group has a whole).
11. The issue of ruggedness of INSAS magazines has been addressed by adopting metal inserts in the plastic magazine.
12. Proprietary rail of INSAS has been dropped in favor ubiquitous picatinny. There seems to be attachment point for fore-grip or bipod stand.
13. The carrying handle and butt trap etc from INSAS system has been dropped and we have bad @ss black color. The problem of handle being too below the barrel in INSAS also seem to have been addressed. Also the issue of feeding lip of magazine also being too low in INSAS, seems to have been addressed. That is rifle seems to more ergonomic and attempt has been made to remove the niggling kinks of INSAS.
14. There may only be a marginal improvement in weight but it seems that not only all the concerns in INSAS have been addressed, we have avoided an over-reach which has been a bug bear of DRDO in other projects.
15. The rifle will be evidently way more costly then INSAS and I wonder whether OFB has a capability to pull up its socks to manufacture such a sophisticated rifle (??).
16. The first pic of MICWS emerged in Ajay Shukla blog. Everybody noted the bullpub but as I pointed out even at that time the conventional rifle was the MCIWS.
pic
17. Incidentally DRDO has been working to improve 5.56mm ammo also, lets see what comes of it.
. Any idea if this is the same UBGL imported to use with AKs/ Tavors? Or indigenous versions?
what about Brahmos-M and shourya ? 
