Second thoughts, I will say this although it contains a bit of a repeat on my part
.
I'm not sure many F1 seasons have seen many of the kind of close competitive team battles that some folk are hoping for. The majority of championships have distilled into a rivalry between just a couple of teams and quite a few down to the punch up between one team's team-mates. The ultimate example of such domination is represented by the McLaren with Senna/Prost domination in 1988 (15 of 16 races), and Ferrari with Schumi/Rubens domination in 2002 (15/17) and 2004 (15/18). However, in the not too distant past for example like Red Bull, Williams and Lotus have had their fair share. So, I think one or two teams rising to the top has always been par for the course.* Having said that the driver "head to heads" within so many teams is a lot more interesting this season.
As I mentioned in another thread, I find this season intriguing because there is so much that can yet happen and a lot of it is in the hands of the engineers. Four races in and I'm still playing catch up with what they're up to as we're only now getting a clearer picture of the technical differences between the cars. So far there have only been a few subtle changes with regard to aero', such as McLaren's nose, but given the three week break I expect to see more (and more obvious) aero' developments show up at the next race.
As has been highlighted by others above, the tighter tracks and races in mixed or wet conditions may well throw up some surprises. It's one thing to have higher top speed but as Red Bull proved time and time again that's only an advantage on the tracks with long straights. Likewise having more power is only an advantage if it can get translated into drive. Any hindrance getting traction means the power advantage can be diminished somewhat - handing advantage back to the guys with better aero' and mechanical grip.
So, the challenge for the rest of the grid is two-fold. They need to get more power out of their power units and more aero' and/or mechanical grip to catch up with Mercedes. Red Bull aren't far off since, as has been said, their down-force looks to be pretty well on a par already. Alonso's Ferrari with him in it has, again as has been noted by others, showed it could mount a pretty good defense against Nico's Merc'.
Whilst I think the championship probably will wind up as a Lewis/Nico head to head it's by no means certain. It is the most likely scenario because of the clever packaging of the Mercedes power unit and power train. I doubt another team can alter theirs this year since it would require radical changes to the chassis not just the mounting of a "split turbo" on the ICE. Therefore their only hope for catch-up, as alluded to by
Mephistopheles , is the law of diminishing returns coming into play, whereby Mercedes may not have as much development room left in the car compared to the rest.
And that's why after a shaky start I'm warming up to this season. After all of the tinkering with rules, tyres and DRS to "spice up the racing" this is actually F1. Technical challenge and mano y mano. I don't mean to be rude but anyone wanting overtaking fest's can
toodle pip and watch NASCAR and dodgems at the fair.
*
Stone me! Apologies for two cliches all in one short sentence 
