Tim Cook will never be as charismatic as Jobs, but let's not forget he's been in holding the reins since even before Jobs' death, and overall he's done a superb job. Probably the most undervalued part of Jobs' legacy was his talent in finding exceptionally gifted people and cementing a company culture that will ensure Apple keeps going strong for many years to come. This isn't to say that if Jobs was still around today he wouldn't be doing a great job, he probably would, but his ego and arrogance sometimes trumped his vision and common sense, and long term that can be really damaging to a company. The new Apple under Cook may not be as flashy as before, but his more rational and open-minded approach will likely be better for the business in the long run.
The big danger here is the Cook has created a situation where Apple is riding on their reputation with policies that produce short term profits only. The warning sign here is they are doing too well. Companies cannot sustain these types of profits, without undermining their long term viability. Cook has managed to antagonise a large amount of the long term user base, and turned a large number users, who would regularly update products, into those who are hanging onto old tech, because the new models are considerably WORSE than the old ones. Take the Mac Mini, with its soldered in memory and total lack of upgradeability. Many users are hanging on to the 2012 model, rather than upgrade because there is no longer an i7 quad core option, and the hard drive and memory cannot be upgraded by users. Other examples are the iMac 21" the latest model of which doesn't even come with a discrete graphics card option, and comes with soldered memory. You can also look at the iPhone and iPads, which have had considerable upgrades to almost every component, but still have a base model with a laughable 16gb of memory. There is the same situation with almost EVERY Apple product, where user upgradeability has been stripped away, so Apple can squeeze a few extra dollars out of users by forcing upgrades through the Apple Store. For things like memory, this forces users to pay 300% of the price for things like memory upgrades, that would previously have been bought elsewhere.
Apple products are also becoming increasingly unrepairable, with so much adhesive being used in their construction that it damages components when they are removed for servicing. Glue is a cheap alternative to screws, and probably saves Apple a few dollars, but it is unacceptable in an upmarket product, which should be as repairable as possible.
I think it is fair to say that a large number of users are fed up with the greed and cheapness that Apple is now displaying. Even some employees at Apple stores have got to the point of questioning decisions over low memory amounts on things like iPhones (though they don't like to admit it), and have fought back over being expected to wait 20 minutes or so to get their bags checked after their shifts have ended.
Apple may be doing well at the moment, but this type of situation cannot last forever and they could be setting up a classic boom/bust situation. While I don't think they will go out of business anytime soon, and I'm not suggesting they will, Apple could easily be on the edge of a major decrease in profits. The fact that sales are decreasing could be an indication of what is to come. Personally, I think the next 5 years or so will be a very interesting time for Apple; it will be interesting to see if they learn from their mistakes, or continue on a course that in time will damage the reputation of the company beyond repair.