AR-15s are everywhere! They have become even more popular in the last decade with the increase of sport shooting like USCA and various steel competitions which allow them. At the same time a trend on the LE/SWAT scene has been in full swing with agencies leaving the MP5s behind and adopting short barreled AR-15s.

The MP5 is a 50 year old platform, but we are starting to see some revived inspiration in the subgun arena. LWRC is a company traditionally known for piston-driven AR-15s, and specialty weapons like the REPR. However, with some inspiration from HK, they have come up with the SMG-45. It even uses UMP magazines! It sports a side-folding stock and just looks SOLID! LWRC produces some of the best quality builds at a great price and I'm sure this will be no exception. From the looks of it, this is the best looking subgun of the bunch. The blend of UMP-like characteristics and AR-15 features make this gun really attractive. At least on paper.

Sig Sauer has jumped on the HK inspired bandwagon as well. The MPX and even MPX-SD is modern-day rendition of the MP5. While the select fire models are only available to GOV/LE, a semi-auto version is also available. However, preliminary reviews showed this gun has some serious issues. The main issue being the pins on the trigger group "walking" out of the receiver. This has led to semi-auto weapons firing multiple rounds per trigger pull. Yikes. Both Sig and LWRC have added AR-like features which are well deserved. Replaceable grips, familiar safety selectors, and bolt releases are all setup like an AR for those familiar with the platform.

CZ has released the Scorpion chambered in 9mm. It has also borrowed the UMP grip angle and safety levers. An ACR-ish stock (on select fire models) and translucent magazines sure look appealing. CZ has incorporated two ways to release the bolt. An HK style cocking handle and an AR-15 style receiver mounted bolt release.

Let's not forget the Kriss Vector which is now producing 9mm versions. Although I'm not a fan of the Vector it's still an innovative design that has no doubt encouraged others companies to look at the subgun market.

I can only speculate on how these guns will do in the GOV/LE markets, but I can't image these companies producing these guns simply for civilian sale so there must be some interest/request for an "updated" MP5.
Personally, I'm a big fan of subguns. Owning both the UMP45 and MP5 I always bring one of the two with me to the range. There is something pleasant about shooting a pistol cartridge from a shoulder fired weapon without the 160+ dB report next to your skull.