Any modern band that comes close to Mahavishnu Orchestra ?

Nothing that I can find.
I love Fusion!  Ever since the old days of listening to Hendrix/Cream/Traffic and the like releasing extended instrumental jams, Fusion seemed like the natural next step in electric instrumental music.  The thing is, while there are many, many musicians with equal chops and intensity, the Mahavishnu Orchestra was lightning in a bottle, not to be replicated or duplicated, EVER!  That said, Fusion has never completely vanished, and while often maligned, there's always lines waiting to get in at shows and thankfully, to this day, there's still great Fusion being created and released.

- Simon Phillips (drums) has recorded a number of great solo Fusion records but has recorded 3 with his band Protocol (2 & 3 are favorites!)

- Gary Willis (bass) is a founding member of one of the greatest 'unknown' Fusion bands ever; Tribal Tech!  He's released a number of sterling Fusionfests but his latest; Larger Than Life, featuring the white-hot Fusion drummer of the moment; Gergo Borlai, is IMO one of the greatest Fusion recordings of the 21st century!

I could truly go on & on but....Nothing solidifies the ongoing popularity of Fusion more than the fact that Al DiMeola's currently on tour (Electric Tour - Elegant Gypsy meets the Romantic Warrior).As is Chick Corea who's recently reformed his Elektric Band for his 75th birthday(!) and started touring this month.  And last but certainly not least is a long rumored supergroup finally performing this month and preparing to tour - Carlos Santana/Wayne Shorter/Herbie Hancock/Marcus Miller/ & Cindy Blackman Santana!  Yeah, we're still flying our Fusion freakflag high!;)  
Tony Williams Lifetime
Alan Holdsworth
The Fents
Return To Forever
Early George Duke
Wishful Thinking
I think The Mahavishnu Orchestra had/has no rivals.  The instrumentation alone makes them completely unique.  The band had a power, an energy and an impact that can't be duplicated.   However, there are fusion elements in the band's works that most fusion bands have.  If you like the soaring energy and the blazing musical speed you might like some of the later King Crimson music (THRAK, THRaKaTTaK, ProjecKts).
Yeah, McLaughlin has no rivals. Back in the 70s he could have assembled one hundred somewhat different Mahavishnu Orchestras and they all would've been excellent or great.
But frankly, to be very impolite, what he has been playing for so many years, with rare exceptions with Shakti, makes no sense and sounds like a screaming of a lonely soul lost in the increasingly incomprehensible wilderness. Even the tone of his supercustom guitars is wrong, I can hear it thru youtube. Not to mention that his bandmates can't play a single note the way it is supposed to be played. Terrible, just terrible. I think, John needs some electroshock therapy. After that either he will start playing what I believe he is still capable of playing or will be gone as a musician altogether. For me either would do but former would definitely be preferred.
Try Steven Wilson. His latest album Hand.Cannot.Erase might be something that you'll like. His albums Grace for Drowning and Raven that refused to sing are also superb. Check out the song Drive Home on Raven. Wait for the guitar solo. If your system can produce deep base all of Wilson's albums have it.