I agree with you that Barcelona will not be able to defend the title this season because Madrid is back with full force to run over Barcelona who dominated the league last season due to the poor condition of Real Madrid squad. The only strong club that played with Barcelona won them last season in the Champions League semifinals. I can't wait to watch the first El Clasico match and let me see what will be the outcome of the game.
The league is more than two El Clasico matches between Barcelona and Real Madrid but after losing all El Clascio matches last season to Barcelona, Real Madrid will no longer want to have another defeat this season. They might also consider that a good result from a first El Clasico in this season will be a quality mark that they are stronger and already competitive enough to beat Barcelona in direct matches and also win La Liga title.
Indeed the current conditions are different where Real Madrid has currently made many improvements, their strength seems to be back in good condition, it can even be said to be much better in the hands of Xabi Alonso but Barcelona also cannot be underestimated even though they have not made many player purchases, their strength in defending the title can still be relied upon, I think the title race will be much more interesting and tight between the two teams.
I believe Real Madrid will have good and considerable improvements as Xabi Alonso is capable do to his mangement well enough. Having considerable improvements than themselves last season is different than winning La Liga title. Real Madrid might become stronger but they will have to compete with other clbs in La Liga especially their likely main competitor Barcelona. They must be stronger than Barcelona and also get more total points in this season than Barcelona in order to win the league trophhy. It's not easy for Real Madrid but they will play matches in this season to win a title, not to finish this season behind Barcelona again.